19396-06-6
YFZNSPMAOIVQRP-YAHZMLKDSA-N
YFZNSPMAOIVQRP-YAHZMLKDSA-N
Polyoxin B
b-D-Allofuranuronic acid, 5-[[2-amino-5-O-(aminocarbonyl)-2-deoxy-L-xylonoyl]amino]-1,5-dideoxy-1-[3,4-dihydro-5-(hydroxymethyl)-2,4-dioxo-1(2H)-pyrimidinyl]-
DTXSID3058329
59456-70-1
WWJFFVUVFNBJTN-UIBIZFFUSA-N
WWJFFVUVFNBJTN-UIBIZFFUSA-N
Nikkomycins
β-D-Allofuranuronic acid, 5-[[(2S,3S,4S)-2-amino-4-hydroxy-4-(5-hydroxy-2-pyridinyl)-3-methyl-1-oxobutyl]amino]-1,5-dideoxy-1-(3,4-dihydro-2,4-dioxo-1(2H)-pyrimidinyl)-
DTXSID5058436
133-06-2
LDVVMCZRFWMZSG-UHFFFAOYNA-N
LDVVMCZRFWMZSG-UHFFFAOYSA-N
Captan
Merpan
1H-Isoindole-1,3(2H)-dione, 3a,4,7,7a-tetrahydro-2-[(trichloromethyl)thio]-
1,2,3,6-Tetrahydro-N-(trichloromethylthio)phthalimide
3a,4,7,7a-Tetrahydro-2-((trichloromethyl)thio)-1H-isoindole-1,3(2H)-dione
3a,4,7,7a-Tetrahydro-2-[(trichloromethyl)thio]-1H-isoindole-1,3(2H)-dione
4-Cyclohexene-1,2-dicarboximide, N-[(trichloromethyl)thio]-
Aacaptan
Amercide
Bangtan
Bangton
Buvisild K
Captadin
Captan [1H-Isoindole-1,3(2H)-dione, 3a,4,7,7a-tetrahydro-2-[(trichloromethyl)thio]-]
Captane
Esso fungicide 406
Fungus Ban Type II
Glyodex 37-22
Hexacap
IH-Isoindole-1,3(2H)-dione,3a,4,7,7a-tetrahydro-2 -[(trichloromethyl)thio]
ISOINDOLE(1H)-1,3(2H)-DIONE, 3A,4,7,7A-TETRAHYDRO-2-[(TRICHLOROMETHYL)THIO]-
Kaptazor
Malipur
Micro-Chek 12
N-[(Trichloromethyl)thio]-4-cyclohexene-1,2-dicarboximide
N-[(Trichloromethyl)thio]tetrahydrophthalimide
N-[(Trichloromethyl)thio]-Δ4-tetrahydrophthalimide
Neracid
NSC 36726
N-Trichloromethylmercapto-4-cyclohexene-1,2-dicarboximide
N-Trichloromethylthio-3a,4,7,7a-tetrahydrophthalimide
N-Trichloromethylthio-4-cyclohexene-1,2-dicarboximide
N-trichloromethylthio-4-cyclohexene-1,2-dicarboxyimide
Orthocide
Orthocide 406
Orthocide 50
Orthocide 7.5
Orthocide 75
Orthocide 75W
Orthocide 83
Orthocide 83RP
Orthocide S 50
Osocide
Radocaptan
Rallis captaf
Stauffer captan
Trimegol
Vancide 89RE
Vangard K
Venturin
Zenecal
DTXSID9020243
2425-06-1
JHRWWRDRBPCWTF-UHFFFAOYNA-N
JHRWWRDRBPCWTF-UHFFFAOYSA-N
Captafol
1H-Isoindole-1,3(2H)-dione, 3a,4,7,7a-tetrahydro-2-[(1,1,2,2-tetrachloroethyl)thio]-
3a,4,7,7a-Tetrahydro-N-(1,1,2,2-tetrachloroethanesulphenyl)phthalimide
4-Cyclohexene-1,2-dicarboximide, N-[(1,1,2,2-tetrachloroethyl)thio]-
Alfloc 7020
Alfloc 7046
Arborseal
Difolatan
Difolatan 4F
Difolatan 4F1
Difolatan 80W
Difolatan BOW
Merpafol
N-(1,1,2,2-Tetrachloroethylthio)-4-cyclohexene-1,2-dicarboximide
N-(1,1,2,2-Tetrachloroethylthio)-4-cyclohexene-1,2-dicarboxyimide
N-(1,1,2,2-Tetrachloroethylthio)cyclohex-4-ene-1,2-dicarboximide
N-(1,1,2,2-Tetrachloroethylthio)-Δ4-tetrahydrophthalimide
N-(Tetrachloroethylthio)tetrahydrophthalimide
N-[(1,1,2,2-Tetrachloroethyl)thio]cyclohex-4-ene-1,2-dicarboximide
N-1,1,2,2-Tetrachloroethylmercapto-4-cyclohexene-1,2-dicarboximide
Proxel EF
Sanspor
Santar SM
Terrazol
Tetrachloroethylthiotetrahydrophthalimide
DTXSID4020242
133-07-3
HKIOYBQGHSTUDB-UHFFFAOYSA-N
HKIOYBQGHSTUDB-UHFFFAOYSA-N
Folpet
Folpan) (N-(Trichloromethylthio)phthalimide
1H-Isoindole-1,3(2H)-dione, 2-[(trichloromethyl)thio]-
2-[(Trichloromethyl)thio]-1H-isoindole-1,3-(2H)-dione
2-[(Trichloromethyl)thio]-1H-isoindole-1,3(2H)-dione
Acryptane
Cosan T
Fungitrol 11
Intercide TMP
N-(Trichlormethylthio)phthalimid
N-(Trichloromethylthio)phtalimide
N-(trichloromethylthio)phthalimide
N-(triclorometiltio)ftalimida
N-[(Trichloromethyl)thio]phthalimide
Orthofaltan 50
Orthophaltan
Phaltan
Phaltane
PHTHALIMIDE, N-[(TRICHLOROMETHYL)THIO]-
Phthaltan
Spolacid
Vinicoll
DTXSID0021385
UBERON:0001002
cuticle
GO:0004100
chitin synthase activity
GO:0042335
cuticle development
GO:0018990
ecdysis, chitin-based cuticle
D009026
mortality
2
decreased
1
increased
Polyoxin B
2018-05-24T15:54:44
2018-05-24T15:54:44
Polyoxin D
2020-10-23T06:20:12
2020-10-23T06:20:12
Nikkomycins
2018-05-24T15:54:09
2018-05-24T15:54:09
Captan
2020-10-23T06:50:43
2020-10-23T06:50:43
Captafol
2020-10-23T06:46:10
2020-10-23T06:52:29
Folpet
2020-10-23T06:53:39
2020-10-23T06:53:39
WCS_7165
Anopheles gambiae
7070
Tribolium castaneum
7111
Trichoplusia ni
7123
Hyalophora cecropia
35572
Bradysia hygida
55057
Mamestra brassicae
168631
Chilo suppressalis
7004
Locusta migratoria
108931
Nilaparvata lugens
307491
Aphis glycines
72036
Lepeophtheirus salmonis
50023
Panonychus citri
192188
Grapholita molesta
248899
Ectropis obliqua
158387
Tigriopus japonicus
7116
Pieris brassicae
7375
Lucilia cuprina
7091
Bombyx mori
85549
Artemia salina
29057
Ostrinia nubilalis
WCS_35525
Daphnia magna
7166
Anopheles quadrimaculatus
WCS_35525
crustaceans
WikiUser_5
insects
Inhibition, Chitin synthase 1
Inhibition, CHS-1
Molecular
<p><span style="font-size:14px">Chitin synthases are essential enzymes for all organisms synthesizing chitin, for example arthropods and fungi (Latgé 2007; Merzendorfer 2011). Chitin synthases polymerize chitin and subsequently translocate chitin through the cell membrane (Merzendorfer 2006; Merzendorfer 2011). In arthropods, two isoforms of the chitin synthase are known, CHS1, which is responsible for the synthesis of cuticular chitin, and chitin synthase isoform 2, which synthesizes chitin in the midgut (Arakane et al. 2005). In this MIE, inhibition of CHS-1 is characterized. The biological state being measured is the activity of the enzyme. CHS-1 has an essential role in the cuticle biology, as it constitutes the last and most critical step in the chitin biosynthetic pathway by catalyzing the polymerization of UDP-GlcNAc to chitin (Merzendorfer and Zimoch 2003; Merzendorfer 2006).</span></p>
<p><span style="font-size:14px">Since the purification or even recombinant production of CHS-1 has not been achieved yet, the most common way is to use crude enzyme preparations for CHS-1 activity assays. It is noteworthy that in crude enzyme preparations of whole organisms both CHS isoforms, CHS-1 and CHS-2, are present. However, the expression of CHS-1 was shown to be much higher than CHS-2 in <em>Anopheles gambiae </em>(Zhang et al. 2012), therefore the effect of CHS-2 may be regarded as negligible. Alternatively, the digestive tract of the respective organism could be removed before producing the enzyme preparation. Different ways exist to detect the activity of the enzyme. One can incubate the enzyme preparation with radioactively labelled chitin precursors (e.g. 14C-UDP-GlcNAc) and measure radioactivity in the formed chitin chains by scintillation counting (Cohen 1982; Cohen and Casida 1990). Chitin synthase activity can also be measured in a non-radioactive way after the addition of precursors to a crude enzyme extract. There, the detection of CHS-1 activity involves the binding of chitin chains to wheat germ agglutinin (WGA) which possesses specific chitin binding properties (Lucero et al. 2002; Zhang and Yan Zhu 2013). The assay builds on the principle of a sandwich-ELISA, where chitin binds to a layer of WGA. A second layer of WGA which is conjugated to horseradish peroxidase (HRP) is then added and subsequently incubated with a HRP substrate. The cleavage of the HRP substrate leads to color formation and the amount of chitin synthesized can be determined colorimetrically.</span></p>
<p><span style="font-size:14px"><strong>Taxonomic: </strong>Effect data for the occurrence of CHS1 inhibition exist from Dipteran, Lepidopteran and Coleopteran insect species. Sequence alignment of CHS1 protein sequences using the Sequence Alignment to Predict Across Species Susceptibility (SeqAPASS, <a href="https://seqapass.epa.gov/seqapass/info.xhtml">https://seqapass.epa.gov/seqapass</a>) tool, yielded susceptibility predictions for various insect species, arachnids and crustacean taxa such as branchiopods, hexanauplia, malocostraca and merostomata. However, most of the protein sequences were not identified as CHS1. The alignment of amino acid residues believed to be critical for ligand binding were therefore carried out with sequences identified as CHS1. Evidence was rated as high for species with a susceptibility prediction and effect data. Evidence was rated as moderate when only alignment data were available. Although most of the sequences are not annotated as CHS1, all arthropods rely on the synthesis of cuticular chitin therefore it is extremely likely that this MIE is applicable to the whole phylum of arthropods.</span></p>
<p><span style="font-size:14px"><strong>Life stage: </strong>This MIE is applicable for organisms undergoing continuous molt cycles. Namely larval stages of insects and all life stages of crustaceans and arachnids.</span></p>
<p><span style="font-size:14px"><strong>Sex: </strong>The MIE is applicable to all sexes.</span></p>
<p><span style="font-size:14px"><strong>Chemical:</strong> Substances known to trigger inhibit CHS-1 are of the family of pyrimidine nucleosides (e.g. polyoxin D, polyoxin B and nikkomycin Z) (Cohen and Casida 1982; Kuwano and Cohen 1984; Cohen and Casida 1990; Zhang and Yan Zhu 2013; Osada 2019). There also exists evidence for the phthalimide captan to inhibit CHS-1 activity <em>in vitro</em> (Cohen and Casida 1982). However, as phthalimides are known to covalently bind to thiol groups in proteins (Lukens and Sisler 1958), it is not clear if the inhibition is due to specific CHS-1 inhibition or due to unspecific protein binding.</span></p>
UBERON:0000483
epithelium
CL:0000658
cuticle secreting cell
Moderate
Unspecific
High
Larvae
High
Juvenile
Moderate
Adult
High
High
High
High
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
<p><span style="font-size:14px">Arakane Y, Muthukrishnan S, Kramer KJ, Specht CA, Tomoyasu Y, Lorenzen MD, Kanost M, Beeman RW. 2005. The <em>Tribolium </em> chitin synthase genes TcCHS1 and TcCHS2 are specialized for synthesis of epidermal cuticle and midgut peritrophic matrix. Insect Mol Biol. 14(5):453–463. doi:10.1111/j.1365-2583.2005.00576.x.</span></p>
<p><span style="font-size:14px">Cohen E. 1982. In vitro chitin synthesis in an insect: formation and structure of microfibrils. Eur J Cell Biol. 26(2):289–294.</span></p>
<p><span style="font-size:14px">Cohen E, Casida JE. 1982. Properties and inhibition of insect integumental chitin synthetase. Pestic Biochem Physiol. 17(3):301–306. doi:10.1016/0048-3575(82)90141-9.</span></p>
<p><span style="font-size:14px">Cohen E, Casida JE. 1990. Insect and Fungal Chitin Synthetase Activity: Specificity of Lectins as Enhancers and Nucleoside Peptides as Inhibitors. Pestic Biochem Physiol. 37(3):249–253. doi:10.1016/0048-3575(90)90131-K.</span></p>
<p><span style="font-size:14px">Kuwano E, Cohen E. 1984. The use of a <em>Tribolium</em> chitin synthetase assay in studying the effects of benzimidazoles with a terpene moiety and related compounds. Agric Biol Chem. 48(6):1617–1620. doi:10.1080/00021369.1984.10866362.</span></p>
<p><span style="font-size:14px">Latgé JP. 2007. The cell wall: A carbohydrate armour for the fungal cell. Mol Microbiol. 66(2):279–290. doi:10.1111/j.1365-2958.2007.05872.x.</span></p>
<p><span style="font-size:14px">Lucero HA, Kuranda MJ, Bulik DA. 2002. A nonradioactive, high throughput assay for chitin synthase activity. Anal Biochem. 305(1):97–105. doi:10.1006/abio.2002.5594.</span></p>
<p><span style="font-size:14px">Lukens RJ, Sisler HD. 1958. 2-Thiazolidinethione-4-carboxylic acid from the reaction of captan with cysteine. Science (80- ). 127(3299):650. doi:10.1126/science.127.3299.650.</span></p>
<p><span style="font-size:14px">Merzendorfer H. 2006. Insect chitin synthases: A review. J Comp Physiol B Biochem Syst Environ Physiol. doi:10.1007/s00360-005-0005-3.</span></p>
<p><span style="font-size:14px">Merzendorfer H. 2011. The cellular basis of chitin synthesis in fungi and insects: Common principles and differences. Eur J Cell Biol. 90(9):759–769. doi:10.1016/j.ejcb.2011.04.014. http://dx.doi.org/10.1016/j.ejcb.2011.04.014.</span></p>
<p><span style="font-size:14px">Merzendorfer H, Zimoch L. 2003. Chitin metabolism in insects: structure, function and regulation of chitin synthases and chitinases. J Exp Biol. 206(24):4393 LP – 4412. doi:10.1242/jeb.00709. http://jeb.biologists.org/content/206/24/4393.abstract.</span></p>
<p><span style="font-size:14px">Osada H. 2019. Discovery and applications of nucleoside antibiotics beyond polyoxin. J Antibiot (Tokyo). 72(12):855–864. doi:10.1038/s41429-019-0237-1. http://dx.doi.org/10.1038/s41429-019-0237-1.</span></p>
<p><span style="font-size:14px">Zhang X, Yan Zhu K. 2013. Biochemical characterization of chitin synthase activity and inhibition in the African malaria mosquito, <em>Anopheles gambiae</em>. Insect Sci. 20(2):158–166. doi:10.1111/j.1744-7917.2012.01568.x.</span></p>
<p><span style="font-size:14px">Zhang X, Zhang J, Park Y, Zhu KY. 2012. Identification and characterization of two chitin synthase genes in African malaria mosquito, Anopheles gambiae. Insect Biochem Mol Biol. 42(9):674–682. doi:10.1016/j.ibmb.2012.05.005. http://dx.doi.org/10.1016/j.ibmb.2012.05.005.</span></p>
2018-05-24T15:57:17
2021-02-24T04:41:51
Decrease, Cuticular chitin content
Decrease, Cuticular chitin content
Tissue
<p><span style="font-size:14px">This key event describes the decrease in cuticular chitin content. Chitin is a major part of the arthropod cuticle and therefore also responsible for its integrity <!--[if supportFields]><span
lang=EN-US style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA'><span style='mso-element:field-begin;mso-field-lock:
yes'></span>ADDIN CSL_CITATION
{"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1002/ps.2780200207","ISSN":"10969063","abstract":"The
functions, structure and biochemistry of the insect cuticle in relation to the
moulting cycle are briefly reviewed as an introduction to the actions of
insecticides that act on the cuticle, particularly acylureas. The symptoms of
poisoning with diflubenzuron (DFB) and other acylureas are consistent with
ultra‐structural and biochemical evidence that these insecticides inhibit the
formation of chitin microfibrils in newly synthesised cuticle. It is probable
that DFB acts at a late stage in chitin biosynthesis, perhaps inhibiting chitin
synthase (CS) itself. However, the results of studies using cell‐free
preparations of CS have not, on the whole, supported this hypothesis. A number
of alternative suggestions as to the mode of action of DFB are reviewed. Among
the most attractive of these is the possibility that DFB may inhibit the
transmembrane transport of chitin synthesis precursors from their site of
production within the epidermal cells to the site of the final poly
condensation reaction, presumably at the apical membrane of the epidermal
microvilli. Copyright © 1987 John Wiley & Sons,
Ltd","author":[{"dropping-particle":"","family":"Reynolds","given":"Stuart
E.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Pesticide
Science","id":"ITEM-1","issue":"2","issued":{"date-parts":[["1987"]]},"page":"131-146","title":"The
cuticle, growth and moulting in insects: The essential background to the action
of acylurea
insecticides","type":"article-journal","volume":"20"},"uris":["http://www.mendeley.com/documents/?uuid=7d4a05a8-c824-42b6-9bf5-c305a2bcfc03"]},{"id":"ITEM-2","itemData":{"DOI":"10.1016/B978-0-12-384747-8.10007-8","ISBN":"9780123847478","abstract":"This
chapter highlights some of the recent and important findings obtained from
studies conducted on the synthesis, structure, physical state, modification,
organization, and degradation of chitin in insect tissues, as well as the
interplay of chitin with chitin-binding proteins, the regulation of genes
responsible for chitin metabolism, and, finally, the targeting of chitin
metabolism for insect-control purposes. Chitin is the major polysaccharide
present in insects and many other invertebrates as well as in several microbes,
including fungi. It serves as the skeletal polysaccharide of several animal
phyla, such as the Arthropoda, Annelida, Molluska, and Coelenterata. In several
groups of fungi, chitin replaces cellulose as the structural polysaccharide. In
insects, it is found in the body wall or cuticle, gut lining or peritrophic
matrix (PM), salivary gland, trachea, eggshells, and muscle attachment points.
In the course of evolution, insects have made excellent use of the rigidity and
chemical stability of the polymeric chitin to assemble both hard and soft
extracellular structures such as the cuticle (exoskeleton) and PM respectively,
both of which enable insects to be protected from the environment while
allowing for growth, mobility, respiration, and communication. All of these
structures are primarily composites of chitin fibers and proteins with varying
degrees of hydration and trace materials distributed along the structures. ©
2012 Elsevier B.V. All rights
reserved.","author":[{"dropping-particle":"","family":"Muthukrishnan","given":"Subbaratnam","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Merzendorfer","given":"Hans","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Arakane","given":"Yasuyuki","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Kramer","given":"Karl
J.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Insect
Molecular Biology and
Biochemistry","id":"ITEM-2","issued":{"date-parts":[["2012"]]},"number-of-pages":"193-235","publisher":"Elsevier
B.V.","title":"Chitin Metabolism in
Insects","type":"book"},"uris":["http://www.mendeley.com/documents/?uuid=24c204e2-9cb5-413f-81eb-5a90926cf1ed"]}],"mendeley":{"formattedCitation":"(Reynolds
1987; Muthukrishnan et al.
2012)","plainTextFormattedCitation":"(Reynolds 1987;
Muthukrishnan et al.
2012)","previouslyFormattedCitation":"[1],
[2]"},"properties":{"noteIndex":0},"schema":"https://github.com/citation-style-language/schema/raw/master/csl-citation.json"}<span
style='mso-element:field-separator'></span></span><![endif]-->(Reynolds 1987; Muthukrishnan et al. 2012)<!--[if supportFields]><span
lang=EN-US style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA'><span style='mso-element:field-end'></span></span><![endif]-->. The cuticle is the exoskeleton of arthropods and has manifold functions, it protects organisms from predators, loss of water, acts as a physical barrier against microbial pathogens and provides support for muscular function <!--[if supportFields]><span
lang=EN-US style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA;mso-bidi-font-weight:bold'><span
style='mso-element:field-begin;mso-field-lock:yes'></span>ADDIN CSL_CITATION
{"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1016/j.asd.2004.05.006","ISSN":"14678039","abstract":"Since
nearly all adult insects fly, the cuticle has to provide a very efficient and
lightweight skeleton. Information is available about the mechanical properties
of cuticle - Young's modulus of resilin is about 1 MPa, of soft cuticles about
1kPa to 50 MPa, of sclerotised cuticles 1-20 GPa; Vicker's Hardness of
sclerotised cuticle ranges between 25 and 80kgfmm-2; density is 1-1.3 kg m-3 -
and one of its components, chitin nanofibres, the Young's modulus of which is
more than 150 GPa. Experiments based on fracture mechanics have not been
performed although the layered structure probably provides some toughening. The
structural performance of wings and legs has been measured, but our
understanding of the importance of buckling is lacking: it can stiffen the
structure (by elastic postbuckling in wings, for example) or be a failure mode.
We know nothing of fatigue properties (yet, for instance, the insect wing must
undergo millions of cycles, flexing or buckling on each cycle). The remarkable
mechanical performance and efficiency of cuticle can be analysed and compared
with those of other materials using material property charts and material
indices. Presented in this paper are four: Young's modulus - density (stiffness
per unit weight), specific Young's modulus - specific strength (elastic hinges,
elastic energy storage per unit weight), toughness - Young's modulus (fracture
resistance under various loading conditions), and hardness (wear resistance).
In conjunction with a structural analysis of cuticle these charts help to
understand the relevance of microstructure (fibre orientation effects in
tendons, joints and sense organs, for example) and shape (including surface
structure) of this fibrous composite for a given function. With modern
techniques for analysis of structure and material, and emphasis on
nanocomposites and self-assembly, insect cuticle should be the archetype for
composites at all levels of scale. © 2004 Elsevier Ltd. All rights
reserved.","author":[{"dropping-particle":"","family":"Vincent","given":"Julian
F.V.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Wegst","given":"Ulrike
G.K.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Arthropod
Structure and Development","id":"ITEM-1","issue":"3","issued":{"date-parts":[["2004"]]},"page":"187-199","title":"Design
and mechanical properties of insect
cuticle","type":"article-journal","volume":"33"},"uris":["http://www.mendeley.com/documents/?uuid=0a16940f-fa66-43c3-8dc5-a683f3a36ac4"]}],"mendeley":{"formattedCitation":"(Vincent
and Wegst 2004)","plainTextFormattedCitation":"(Vincent and
Wegst
2004)","previouslyFormattedCitation":"[3]"},"properties":{"noteIndex":0},"schema":"https://github.com/citation-style-language/schema/raw/master/csl-citation.json"}<span
style='mso-element:field-separator'></span></span><![endif]-->(Vincent and Wegst 2004)<!--[if supportFields]><span
lang=EN-US style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA;mso-bidi-font-weight:bold'><span
style='mso-element:field-end'></span></span><![endif]-->. Hence, cuticular chitin is also indispensable for the development of arthropods, as an immaculate cuticle is required for proper molting and therefore also for the growth of an organism.</span><br />
</p>
<p><span style="font-size:14px">Several ways to determine cuticular chitin are described in the literature. Some of them are based on the determination of amino sugars after digestion or hydrolysis of chitin. For example, after the digestion of chitin by a bacterial chitinase, the <em>N</em>-Acetylclucosamine (GlcNAc) amount can be determined colorimetrically by a modified Morgan-Elson assay <!--[if supportFields]><span lang=EN-US style='font-size:11.0pt;
line-height:107%;font-family:"Calibri",sans-serif;mso-ascii-theme-font:minor-latin;
mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;mso-hansi-theme-font:
minor-latin;mso-bidi-font-family:"Times New Roman";mso-bidi-theme-font:minor-bidi;
mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA'><span
style='mso-element:field-begin;mso-field-lock:yes'></span>ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"author":[{"dropping-particle":"","family":"Reissig","given":"J.
L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Strominger","given":"J.
L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Leloir","given":"L.
F.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"The
Journal of Biological
Chemistry","id":"ITEM-1","issued":{"date-parts":[["1955"]]},"page":"959-966","title":"A
modified colorimetric method for the estimation of N-acetylamino
sugars","type":"article-journal"},"uris":["http://www.mendeley.com/documents/?uuid=e5b7080f-7220-4ac0-91fe-53323221ce31"]},{"id":"ITEM-2","itemData":{"DOI":"10.1111/j.1365-2583.2005.00576.x","ISSN":"09621075","PMID":"16164601","abstract":"Functional
analysis of the two chitin synthase genes, TcCHS1 and TcCHS2, in the red flour
beetle, Tribolium castaneum, revealed unique and complementary roles for each
gene. TcCHS1-specific RNA interference (RNAi) disrupted all three types of
moult (larval-larval, larval-pupal and pupal-adult) and greatly reduced
whole-body chitin content. Exon-specific RNAi showed that splice variant 8a of
TcCHS1 was required for both the larval-pupal and pupal-adult moults, whereas
splice variant 8b was required only for the latter. TcCHS2-specific RNAi had no
effect on metamorphosis or on total body chitin content. However, RNAi-mediated
down-regulation of TcCHS2, but not TcCHS1, led to cessation of feeding, a
dramatic shrinkage in larval size and reduced chitin content in the midgut. ©
2005 The Royal Entomological
Society.","author":[{"dropping-particle":"","family":"Arakane","given":"Y.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Muthukrishnan","given":"S.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Kramer","given":"K.
J.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Specht","given":"C.
A.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Tomoyasu","given":"Y.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Lorenzen","given":"M.
D.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Kanost","given":"M.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Beeman","given":"R.
W.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Insect
Molecular
Biology","id":"ITEM-2","issue":"5","issued":{"date-parts":[["2005"]]},"page":"453-463","title":"The
<i>Tribolium </i> chitin synthase genes TcCHS1 and TcCHS2 are
specialized for synthesis of epidermal cuticle and midgut peritrophic
matrix","type":"article-journal","volume":"14"},"uris":["http://www.mendeley.com/documents/?uuid=849047b2-43cc-4c68-a566-ac8d02770f8f"]}],"mendeley":{"formattedCitation":"(Reissig
et al. 1955; Arakane et al.
2005)","plainTextFormattedCitation":"(Reissig et al. 1955;
Arakane et al. 2005)","previouslyFormattedCitation":"[9],
[10]"},"properties":{"noteIndex":0},"schema":"https://github.com/citation-style-language/schema/raw/master/csl-citation.json"}<span
style='mso-element:field-separator'></span></span><![endif]-->(Reissig et al. 1955; Arakane et al. 2005)<!--[if supportFields]><span
lang=EN-US style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA'><span style='mso-element:field-end'></span></span><![endif]-->. Alternatively, one can also quantify glucosamine colorimetrically after deacetylation and hydrolysis of chitin <!--[if supportFields]><span lang=EN-US
style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA;mso-no-proof:yes'><span style='mso-element:field-begin;
mso-field-lock:yes'></span>ADDIN CSL_CITATION
{"citationItems":[{"id":"ITEM-1","itemData":{"author":[{"dropping-particle":"","family":"Lehmann","given":"Paul
F.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"White","given":"Les
O.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Infection
and
immunity","id":"ITEM-1","issue":"5","issued":{"date-parts":[["1975"]]},"page":"987-992","title":"Chitin
Assay Used to Demonstrate Renal Localization and Cortisone-Enhanced Growth of
<i>Aspergillus fumigatus</i> Mycelium in
Mice","type":"article-journal","volume":"12"},"uris":["http://www.mendeley.com/documents/?uuid=9a283039-39e3-4744-ad55-257699c604a7"]},{"id":"ITEM-2","itemData":{"DOI":"10.1016/j.ibmb.2006.06.002","ISSN":"09651748","abstract":"Chitin
synthase (EC 2.4.1.16) is a crucial enzyme responsible for chitin biosynthesis
in all chitin-containing organisms. This paper reports a complete cDNA encoding
chitin synthase 1 (AqCHS1), change of AqCHS1 mRNA level in response to
diflubenzuron exposure, and concentration-dependent effect of diflubenzuron on
chitin synthesis in the common malaria mosquito (Anopheles quadrimaculatus).
The cDNA consists of 5723 nucleotides, including an open reading frame (ORF) of
4734 nucleotides that encode 1578 amino acid residues and a non-translated
region of 989 nucleotides. The deduced amino acid sequence contains all the
chitin synthase signature motifs (EDR, QRRRW and SWGTR) and shows 97% identity
to that of An. gambiae (AgCHS1, XM_321337). Northern blot and real-time
quantitative PCR analyses revealed a significant increase of AqCHS1 mRNA level
in the larvae exposed to diflubenzuron at 100 and 500 μg/L. As confirmed by
real-time quantitative PCR, AqCHS1 mRNA level was enhanced by 2-fold in the
larvae exposed to diflubenzuron at 500 μg/L for 24 h. In contrast, exposures of
the larvae to diflubenzuron at 4.0, 20, 100 and 500 μg/L for 48 h resulted in
decreases of chitin content by 9.0%, 43%, 58% and 76%, respectively.
Significantly increased AqCHS1 mRNA level associated with decreased chitin
synthesis may imply possible inhibition of chitin synthase, or abnormal chitin
synthase translocation or chitin microfibril assembly conferred by
diflubenzuron. Increased AqCHS1 expression due to increased transcription
and/or increased mRNA stability may serve as a feedback mechanism to compensate
such an effect in the mosquitoes. Further studies are necessary to elucidate
the relationship between reduced chitin synthesis and increased expression of
AqCHS1 in order to shed new light on trafficking and regulation of chitin biosynthesis
in the mosquito affected by diflubenzuron. © 2006 Elsevier Ltd. All rights
reserved.","author":[{"dropping-particle":"","family":"Zhang","given":"Jianzhen","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Zhu","given":"Kun
Yan","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Insect
Biochemistry and Molecular Biology","id":"ITEM-2","issue":"9","issued":{"date-parts":[["2006"]]},"page":"712-725","title":"Characterization
of a chitin synthase cDNA and its increased mRNA level associated with
decreased chitin synthesis in <i>Anopheles quadrimaculatus</i>
exposed to
diflubenzuron","type":"article-journal","volume":"36"},"uris":["http://www.mendeley.com/documents/?uuid=fa5bf775-1428-4062-8648-d40302face64"]}],"mendeley":{"formattedCitation":"(Lehmann
and White 1975; Zhang and Zhu
2006)","plainTextFormattedCitation":"(Lehmann and White
1975; Zhang and Zhu 2006)","previouslyFormattedCitation":"[11],
[12]"},"properties":{"noteIndex":0},"schema":"https://github.com/citation-style-language/schema/raw/master/csl-citation.json"}<span
style='mso-element:field-separator'></span></span><![endif]-->(Lehmann and White 1975; Zhang and Zhu 2006)<!--[if supportFields]><span lang=EN-US style='font-size:
11.0pt;line-height:107%;font-family:"Calibri",sans-serif;mso-ascii-theme-font:
minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:minor-latin;
mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA;mso-no-proof:yes'><span style='mso-element:field-end'></span></span><![endif]-->.<br />
There also exists an approach based on the detection of fluorescence after staining with calcofluor white. In this assay, no treatment of the samples is necessary, the detection is carried out in homogenates of the respective organisms as calcofluor white directly binds to chitin <!--[if supportFields]><span
lang=EN-US style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA;mso-no-proof:yes'><span style='mso-element:field-begin;
mso-field-lock:yes'></span>ADDIN CSL_CITATION {"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.3389/fphys.2020.00117","ISSN":"1664042X","abstract":"Chitin
is an aminopolysaccharide present in yeast cells and arthropod cuticle and is
one of the most abundant biopolymers. The conventional methods for the
quantitation of chitin content in biological samples are based on its
hydrolysis (acid or enzymatic), and the assessment of the byproduct,
glucosamine. However, previously described methodologies are time-consuming,
laborious, low throughput, and not applicable to insect samples in many cases.
Here we describe a new approach to chitin content quantitation based on
calcofluor fluorescent brightener staining of samples, followed by microplate
fluorescence readings. Calcofluor is a specific chitin stain commonly used for
topological localization of the polymer. The protocol was tested in three
important disease vector species, namely Lutzomyia longipalpis, Aedes aegypti,
and Rhodnius prolixus, and then compared to a classic colorimetric chitin
assessment method. Results show that chitin content in the tested insects can
vary largely in a range of 8–4600 micrograms of chitin per insect, depending on
species, sex, and instar. Comparisons between measurements from the previous
protocol and calcofluor method showed statistically significant differences in
some samples. However, the difference might be due to interference in the
classic method from non-chitin sources of glucosamine and reducing agents.
Furthermore, chitinase hydrolysis reduces the total chitin mass estimated
between 36 and 74%, consolidating the fluorescent measurements as actual
stained chitin in the same extent that was observed with the standard protocol.
Therefore, the calcofluor staining method revealed to be a fast and reliable
technique for chitin quantitation in homogenized insect
samples.","author":[{"dropping-particle":"","family":"Henriques","given":"Bianca
Santos","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Garcia","given":"Eloi
Souza","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Azambuja","given":"Patricia","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Genta","given":"Fernando
Ariel","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Frontiers
in
Physiology","id":"ITEM-1","issue":"February","issued":{"date-parts":[["2020"]]},"page":"1-10","title":"Determination
of Chitin Content in Insects: An Alternate Method Based on Calcofluor
Staining","type":"article-journal","volume":"11"},"uris":["http://www.mendeley.com/documents/?uuid=e225b750-e330-404b-bc62-3fe4adb45c82"]}],"mendeley":{"formattedCitation":"(Henriques
et al. 2020)","plainTextFormattedCitation":"(Henriques et
al.
2020)","previouslyFormattedCitation":"[13]"},"properties":{"noteIndex":0},"schema":"https://github.com/citation-style-language/schema/raw/master/csl-citation.json"}<span
style='mso-element:field-separator'></span></span><![endif]-->(Henriques et al. 2020)<!--[if supportFields]><span
lang=EN-US style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA;mso-no-proof:yes'><span style='mso-element:field-end'></span></span><![endif]-->.<br />
Chitin can also be quantified using radioactively labelled precursors (e.g. 14C-UDP-GlcNAc) which are incorporated into <em>in vitro</em> cultured integument pieces or into the cuticle of whole organisms <!--[if supportFields]><span
lang=EN-US style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA;mso-no-proof:yes'><span style='mso-element:field-begin;
mso-field-lock:yes'></span>ADDIN CSL_CITATION
{"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1016/0048-3575(79)90098-1","ISSN":"10959939","abstract":"The
increase in cuticle thickness with age of fifth instar larvae of Pieris
brassicae (L.) was measured microscopically. The injection of a lethal dose of
either Polyoxin D or diflubenzuron revealed total inhibition of cuticular
growth and caused comparable abnormalities in the cuticles. In a further
experiment [14C]glucose was injected along with Polyoxin D into Pieris
brassicae and the incorporation of radioactivity into various tissue fractions
was measured. This revealed that the impairment of cuticular growth was due to
inhibition of chitin synthesis. With the methods used the effects of Polyoxin D
and two benzoylphenylurea insecticides appeared to be the same. ©
1979.","author":[{"dropping-particle":"","family":"Gijswijt","given":"M.
J.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Deul","given":"D.
H.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Jong","given":"B.
J.","non-dropping-particle":"de","parse-names":false,"suffix":""}],"container-title":"Pesticide
Biochemistry and
Physiology","id":"ITEM-1","issue":"1","issued":{"date-parts":[["1979"]]},"page":"87-94","title":"Inhibition
of chitin synthesis by benzoyl-phenylurea insecticides, III. Similarity in
action in <i>Pieris brassicae</i> (L.) with Polyoxin
D","type":"article-journal","volume":"12"},"uris":["http://www.mendeley.com/documents/?uuid=d8c76ed6-331a-4d84-a384-060a7786c23b"]},{"id":"ITEM-2","itemData":{"DOI":"10.1071/BI9820491","ISSN":"00049417","abstract":"Isolated
whole integuments from L. cuprina larvae rapidly incorporate radioactivity from
both N-acetyl[1-14C]glucosamine and [1-'4C]glucosamine into alkali-insoluble
material, a reaction which does not require preincubation of the tissue with
β-ecdysone. The labelled product was degraded to N-acetylglucosamine during
digestion with chitinase, establishing that it consists mainly of chitin.
Incorporation was inhibited by polyoxin-D (I506 × 10−7 M) and diflubenzuron
(I507 × 10−7 M) but was not inhibited to any marked extent by isoprothiolane,
Vetrazin or α-methyl-DOPA. The effectiveness of diflubenzuron as an inhibitor
of chitin synthesis in this system (I506 × 10−7 M) correlates well with its
potency as a larvicide (LD502 · 1 × 10−6 M), providing additional support for
the proposal that this compound kills larvae by interfering with chitin
deposition in the cuticle. Polyoxin-D was much more effective as an inhibitor
of chitin synthesis (I506 × 10−7 M) than as a larvicide (LD502 · 0 × 10−5 M).
It was established that the final intermediate of chitin biosynthesis
(UDP-N-acetylglucosamine) was formed in the isolated integuments in the
presence of diflubenzuron and polyoxin-D. It seems likely therefore that both
compounds interfere with the final polymerization step of the chitin
biosynthesis pathway. © 1982
ASEG.","author":[{"dropping-particle":"","family":"Turnbull","given":"I.
F.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Howells","given":"A.
J.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Australian
Journal of Biological Sciences","id":"ITEM-2","issue":"5","issued":{"date-parts":[["1982"]]},"page":"491-504","title":"Effects
of several larvicidal compounds on chitin biosynthesis by isolated larval
integuments of the sheep blowfly <i>Lucilia
cuprina</i>","type":"article-journal","volume":"35"},"uris":["http://www.mendeley.com/documents/?uuid=fd6263b3-01b7-4b0e-bbcc-3c62e798badd"]},{"id":"ITEM-3","itemData":{"DOI":"10.7164/antibiotics.37.253","author":[{"dropping-particle":"","family":"Calcott","given":"Peter
H","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Fatig","given":"Raymond
O","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Journal
of
Antibiotics","id":"ITEM-3","issue":"3","issued":{"date-parts":[["1984"]]},"page":"253-259","title":"Inhibition
of Chitin metabolism by Avermectin in susceptible
Organisms","type":"article-journal","volume":"37"},"uris":["http://www.mendeley.com/documents/?uuid=766ef597-d1ad-424e-ab3d-94c8c47a9f89"]},{"id":"ITEM-4","itemData":{"DOI":"10.1016/0742-8413(86)90073-3","ISSN":"03064492","PMID":"2877789","abstract":"1.
1. A rapid, reliable, repeatable bioassay for measuring chitin synthesis is
described. 2. 2. It utilizes the clasper from male pharate adult European corn
borers and measures the incorporation of [14C]N-acetylglucosamine. 3. 3. Chitin
synthesis is maximum in claspers taken from animals 5 and 6 days postpupation.
4. 4. The system is very sensitive to inhibition by the phenylbenzoyl ureas and
polyoxins and should be useful for identifying potential inhibitory agents. ©
1988.","author":[{"dropping-particle":"","family":"Gelman","given":"D.
B.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Borkovec","given":"Alexej
B.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Comparative
Biochemistry and Physiology. Part C,
Comparative","id":"ITEM-4","issue":"1","issued":{"date-parts":[["1986"]]},"page":"193-197","title":"The
pharate adult clasper as a tool for measuring chitin synthesis and for
identifying new chitin synthesis
inhibitors","type":"article-journal","volume":"85"},"uris":["http://www.mendeley.com/documents/?uuid=8f617e22-df7d-4431-a130-09ed71888baa"]}],"mendeley":{"formattedCitation":"(Gijswijt
et al. 1979; Turnbull and Howells 1982; Calcott and Fatig 1984; Gelman and
Borkovec 1986)","plainTextFormattedCitation":"(Gijswijt et
al. 1979; Turnbull and Howells 1982; Calcott and Fatig 1984; Gelman and
Borkovec
1986)","previouslyFormattedCitation":"[14]–[17]"},"properties":{"noteIndex":0},"schema":"https://github.com/citation-style-language/schema/raw/master/csl-citation.json"}<span
style='mso-element:field-separator'></span></span><![endif]-->(Gijswijt et al. 1979; Turnbull and Howells 1982; Calcott and Fatig 1984; Gelman and Borkovec 1986)<!--[if supportFields]><span
lang=EN-US style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA;mso-no-proof:yes'><span style='mso-element:field-end'></span></span><![endif]-->.<br />
Another possibility is to use the non-radioactive assay developed to measure chitin synthase activity (Lucero et al. 2002; Zhang and Yan Zhu 2013). Instead of adding an enzyme extract and chitin precursors to the reaction, one could simply add homogenized chitin containing material to the reaction to quantify its chitin content.</span></p>
<p><span style="font-size:14px"><strong>Taxonomic: </strong>Effect data for the occurrence of this KE exist from <em>Pieris brassicae</em>, <em>Lucilia cuprina</em>, <em>Bombyx mori</em>, <em>Artemia salina</em> and <em>Ostrinia nubilalis</em>, defining its taxonomic applicability. Most likely, this KE is applicable to the whole phylum of arthropods, as they all rely on chitin as part of their exoskeleton.</span></p>
<p><span style="font-size:14px"><strong>Life stage: </strong>This KE is applicable for organisms synthesizing chitin in order to grow and develop, namely larval stages of insects and all life stages of crustaceans and arachnids.</span></p>
<p><span style="font-size:14px"><strong>Sex: </strong>This KE is applicable to all sexes.</span></p>
<p><span style="font-size:14px"><strong>Chemical:</strong> Substances known decrease the cuticular chitin content are of the family of pyrimidine nucleosides (e.g. polyoxin D and nikkomycin Z) (Gijswijt et al. 1979; Turnbull and Howells 1982; Calcott and Fatig 1984; Zhuo et al. 2014; Osada 2019). There also exists evidence for phthalimides (captan, captafol and folpet) to to decrease the cuticular chitin content <em>in vitro</em> (Gelman and Borkovec 1986). However, as these substances are known to covalently bind to thiol groups in proteins (Lukens and Sisler 1958), it is not clear if the inhibition is due to specific CHS-1 inhibition or due to unspecific protein binding.</span></p>
UBERON:0001002
cuticle
Moderate
Unspecific
High
Larvae
High
Juvenile
Moderate
Adult
High
High
High
High
High
<p><span style="font-size:14px">Arakane Y, Muthukrishnan S, Kramer KJ, Specht CA, Tomoyasu Y, Lorenzen MD, Kanost M, Beeman RW. 2005. The <em>Tribolium </em> chitin synthase genes TcCHS1 and TcCHS2 are specialized for synthesis of epidermal cuticle and midgut peritrophic matrix. Insect Mol Biol. 14(5):453–463. doi:10.1111/j.1365-2583.2005.00576.x.</span></p>
<p><span style="font-size:14px">Calcott PH, Fatig RO. 1984. Inhibition of Chitin metabolism by Avermectin in susceptible Organisms. J Antibiot (Tokyo). 37(3):253–259. doi:10.7164/antibiotics.37.253.</span></p>
<p><span style="font-size:14px">Clarke KU. 1957. On the Increase in Linear Size During Growth in <em>Locusta Migratoria</em> L. Proc R Entomol Soc London Ser A, Gen Entomol. 32(1–3):35–39. doi:10.1111/j.1365-3032.1957.tb00361.x.</span></p>
<p><span style="font-size:14px">Dall W, Smith DM, Press B. 1978. Water uptake at ecdysis in the western rock lobster. J Exp Mar Bio Ecol. 35(1960). doi:10.1016/0022-0981(78)90074-6.</span></p>
<p><span style="font-size:14px">deFur PL, Mangum CP, McMahon BR. 1985. Cardiovascular and Ventilatory Changes During Ecdysis in the Blue Crab <em>Callinectes Sapidus</em> Rathbun. J Crustac Biol. 5(2):207–215. doi:10.2307/1547867.</span></p>
<p><span style="font-size:14px">Ewer J. 2005. How the ecdysozoan changed its coat. PLoS Biol. 3(10):1696–1699. doi:10.1371/journal.pbio.0030349.</span></p>
<p><span style="font-size:14px">Gelman DB, Borkovec AB. 1986. The pharate adult clasper as a tool for measuring chitin synthesis and for identifying new chitin synthesis inhibitors. Comp Biochem Physiol Part C, Comp. 85(1):193–197. doi:10.1016/0742-8413(86)90073-3.</span></p>
<p><span style="font-size:14px">Gijswijt MJ, Deul DH, de Jong BJ. 1979. Inhibition of chitin synthesis by benzoyl-phenylurea insecticides, III. Similarity in action in <em>Pieris brassicae</em> (L.) with Polyoxin D. Pestic Biochem Physiol. 12(1):87–94. doi:10.1016/0048-3575(79)90098-1.</span></p>
<p><span style="font-size:14px">Henriques BS, Garcia ES, Azambuja P, Genta FA. 2020. Determination of Chitin Content in Insects: An Alternate Method Based on Calcofluor Staining. Front Physiol. 11(February):1–10. doi:10.3389/fphys.2020.00117.</span></p>
<p><span style="font-size:14px">Lee RM. 1961. The variation of blood volume with age in the desert locust (<em>Schistocerca gregaria</em> Forsk.). J Insect Physiol. 6(1):36–51. doi:10.1016/0022-1910(61)90090-7.</span></p>
<p><span style="font-size:14px">Lehmann PF, White LO. 1975. Chitin Assay Used to Demonstrate Renal Localization and Cortisone-Enhanced Growth of <em>Aspergillus fumigatus</em> Mycelium in Mice. Infect Immun. 12(5):987–992.</span></p>
<p><span style="font-size:14px">Lucero HA, Kuranda MJ, Bulik DA. 2002. A nonradioactive, high throughput assay for chitin synthase activity. Anal Biochem. 305(1):97–105.<br />
doi:10.1006/abio.2002.5594.</span></p>
<p><span style="font-size:14px">Lukens RJ, Sisler HD. 1958. 2-Thiazolidinethione-4-carboxylic acid from the reaction of captan with cysteine. Science (80- ). 127(3299):650. doi:10.1126/science.127.3299.650.</span></p>
<p><span style="font-size:14px">Muthukrishnan S, Merzendorfer H, Arakane Y, Kramer KJ. 2012. Chitin Metabolism in Insects. Elsevier B.V. http://dx.doi.org/10.1016/B978-0-12-384747-8.10007-8.</span></p>
<p><span style="font-size:14px">Osada H. 2019. Discovery and applications of nucleoside antibiotics beyond polyoxin. J Antibiot (Tokyo). 72(12):855–864. doi:10.1038/s41429-019-0237-1. http://dx.doi.org/10.1038/s41429-019-0237-1.</span></p>
<p><span style="font-size:14px">Reissig JL, Strominger JL, Leloir LF. 1955. A modified colorimetric method for the estimation of N-acetylamino sugars. J Biol Chem.:959–966.</span></p>
<p><span style="font-size:14px">Reynolds SE. 1987. The cuticle, growth and moulting in insects: The essential background to the action of acylurea insecticides. Pestic Sci. 20(2):131–146. doi:10.1002/ps.2780200207.</span></p>
<p><span style="font-size:14px">Turnbull IF, Howells AJ. 1982. Effects of several larvicidal compounds on chitin biosynthesis by isolated larval integuments of the sheep blowfly <em>Lucilia cuprina</em>. Aust J Biol Sci. 35(5):491–504. doi:10.1071/BI9820491.</span></p>
<p><span style="font-size:14px">Vincent JFV, Wegst UGK. 2004. Design and mechanical properties of insect cuticle. Arthropod Struct Dev. 33(3):187–199. doi:10.1016/j.asd.2004.05.006.</span></p>
<p><span style="font-size:14px">Zhang J, Zhu KY. 2006. Characterization of a chitin synthase cDNA and its increased mRNA level associated with decreased chitin synthesis in <em>Anopheles quadrimaculatus</em> exposed to diflubenzuron. Insect Biochem Mol Biol. 36(9):712–725. doi:10.1016/j.ibmb.2006.06.002.</span></p>
<p><span style="font-size:14px">Zhang X, Yan Zhu K. 2013. Biochemical characterization of chitin synthase activity and inhibition in the African malaria mosquito, Anopheles<br />
gambiae. Insect Sci. 20(2):158–166. doi:10.1111/j.1744-7917.2012.01568.x.</span></p>
<p><span style="font-size:14px">Zhuo W, Fang Y, Kong L, Li X, Sima Y, Xu S. 2014. Chitin synthase A: A novel epidermal development regulation gene in the larvae of <em>Bombyx mori</em>. Mol Biol Rep. 41(7):4177–4186. doi:10.1007/s11033-014-3288-1.</span></p>
2018-05-24T15:58:20
2021-02-17T05:37:36
Increase, Premature molting
Increase, Premature molting
Individual
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px">This key event is measured on the level of the individual. In order to grow and develop, arthropods need to shed their exoskeleton periodically (molting) (Heming 2018). During molting, the newly secreted cuticle is subject to mechanical stress associated and therefore needs to possess enough structural and functional integrity. The ecdysis motor program, which constitutes the behavioral part of the cuticle shedding requires the newly secreted cuticle to possess a certain strength to support for muscular force in order to shed the old cuticle (Ewer 2005). Cuticular integrity is also important after ecdysis, as insects and crustaceans expand their new cuticle by increasing internal pressure by swallowing air and water, respectively. This happens in order to expand and provide stability to the new cuticle until it is hardened (tanned) (Clarke 1957; Lee 1961; Dall et al. 1978; deFur et al. 1985). If arthropods are not able to molt properly, the organism will eventually die. Premature molting describes the unsuccessful molting where the organism is not able to shed the old cuticle, but also other effects related to molting in an immature stage where the new cuticle is not mature enough for the molt, such as rupture of the new cuticle and associated desiccation, deformities, higher susceptibility to pathogens or impaired locomotion. Specific effects observed are animals stuck in their exuviae (Wang et al., 2019), and if molting can be completed despite an immature cuticle, animals might be smaller and die at subsequent molts (Arakawa et al., 2008; Chen et al., 2008; Mohammed et al., 2017).</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px">Premature molting can be determined by observation. No standardized tests for the endpoint of molting exist to date. However, during an OECD 202 <em>Daphnia</em> sp. Acute immobilization test (OECD 2004), the cumulative number of molts can be assessed as an additional endpoint. Molting can also be assessed during a OECD 211 <em>Daphnia</em> sp. Reproduction test (OECD 2012), as proposed previously (OECD 2003). One could even prolong the test to 96h to get a clearer result of this endpoint. Additionally, one could apply histopathological methods to monitor the maturity of the newly synthesized cuticle (e.g. thickness of procuticle).</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><strong>Taxonomic: </strong>Effect data for the occurrence of this KE exist from <em>Pieris brassicae</em> and <em>Lucilia cuprina</em>. However, all arthropods undergo molting, so it is highly likely that this KE is applicable to the whole phylum of arthropods.</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><strong>Life stage: </strong>This KE is applicable for organisms that undergo molting in order to grow and develop, namely larval stages of insects and all life stages of crustaceans and arachnids.</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><strong>Sex: </strong>This KE is applicable to all sexes.</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><strong>Chemical:</strong> Substances known to induce premature molting are of the family of pyrimidine nucleosides (e.g. polyoxin D and nikkomycin Z) (Gijswijt et al. 1979; Tellam et al. 2000; Arakawa et al. 2008).</span></span></p>
Moderate
Unspecific
High
Larvae
High
Juvenile
Moderate
Adult
High
High
<p><span style="font-size:14px"><span style="font-family:Arial,Helvetica,sans-serif">Arakawa T, Yukuhiro F, Noda H. 2008. Insecticidal effect of a fungicide containing polyoxin B on the larvae of <em>Bombyx mori</em> (Lepidoptera: Bombycidae), <em>Mamestra brassicae</em>, <em>Mythimna separata</em>, and <em>Spodoptera litura</em> (Lepidoptera: Noctuidae). Appl Entomol Zool. 43(2):173–181. doi:10.1303/aez.2008.173.</span></span></p>
<p><span style="font-size:14px"><span style="font-family:Arial,Helvetica,sans-serif">Chen, X.; Tian, H.; Zou, L.; Tang, B.; Hu, J.; Zhang, W. Disruption of Spodoptera Exigua Larval Development by Silencing Chitin Synthase Gene A with RNA Interference. Bull. Entomol. Res. 2008, 98 (6), 613–619. https://doi.org/10.1017/S0007485308005932.</span></span></p>
<p><span style="font-size:14px"><span style="font-family:Arial,Helvetica,sans-serif">Clarke KU. 1957. On the Increase in Linear Size During Growth in Locusta Migratoria L. Proc R Entomol Soc London Ser A, Gen Entomol. 32(1–<br />
3):35–39. doi:10.1111/j.1365-3032.1957.tb00361.x.</span></span></p>
<p><span style="font-size:14px"><span style="font-family:Arial,Helvetica,sans-serif">Dall W, Smith DM, Press B. 1978. Water uptake at ecdysis in the western rock lobster. J Exp Mar Bio Ecol. 35(1960). doi:10.1016/0022-<br />
0981(78)90074-6.</span></span></p>
<p><span style="font-size:14px"><span style="font-family:Arial,Helvetica,sans-serif">deFur PL, Mangum CP, McMahon BR. 1985. Cardiovascular and Ventilatory Changes During Ecdysis in the Blue Crab Callinectes Sapidus<br />
Rathbun. J Crustac Biol. 5(2):207–215. doi:10.2307/1547867.</span></span></p>
<p><span style="font-size:14px"><span style="font-family:Arial,Helvetica,sans-serif">Ewer J. 2005. How the ecdysozoan changed its coat. PLoS Biol. 3(10):1696–1699. doi:10.1371/journal.pbio.0030349.</span></span></p>
<p><span style="font-size:14px"><span style="font-family:Arial,Helvetica,sans-serif">Gijswijt MJ, Deul DH, de Jong BJ. 1979. Inhibition of chitin synthesis by benzoyl-phenylurea insecticides, III. Similarity in action in <em>Pieris brassicae</em> (L.) with Polyoxin D. Pestic Biochem Physiol. 12(1):87–94. doi:10.1016/0048-3575(79)90098-1.</span></span></p>
<p><span style="font-size:14px"><span style="font-family:Arial,Helvetica,sans-serif">Heming BS. 2018. Insect development and evolution. Ithaca: Cornell University Press.</span></span></p>
<p><span style="font-size:14px"><span style="font-family:Arial,Helvetica,sans-serif">Mohammed, A. M. A.; DIab, M. R.; Abdelsattar, M.; Khalil, S. M. S. Characterization and RNAi-Mediated Knockdown of Chitin Synthase A in the Potato Tuber Moth, Phthorimaea Operculella. Sci. Rep. 2017, 7 (1), 1–12. https://doi.org/10.1038/s41598-017-09858-y.</span></span></p>
<p><span style="font-size:14px"><span style="font-family:Arial,Helvetica,sans-serif">Lee RM. 1961. The variation of blood volume with age in the desert locust (Schistocerca gregaria Forsk.). J Insect Physiol. 6(1):36–51.<br />
doi:10.1016/0022-1910(61)90090-7.</span></span></p>
<p><span style="font-size:14px"><span style="font-family:Arial,Helvetica,sans-serif">OECD (2003), Proposal for an Enhanced Test Guideline. Daphnia magna Reproduction Test. Draft OECD Guidel. Test. Chem. Enhanc. Tech. Guid. Doc. 211 21.</span></span></p>
<p><span style="font-size:14px"><span style="font-family:Arial,Helvetica,sans-serif">OECD (2004), <em>Test No. 202: Daphnia sp. Acute Immobilisation Test</em>, OECD Guidelines for the Testing of Chemicals, Section 2, OECD Publishing, Paris, <a href="https://doi.org/10.1787/9789264069947-en" title="">https://doi.org/10.1787/9789264069947-en</a>.</span></span></p>
<p><span style="font-size:14px"><span style="font-family:Arial,Helvetica,sans-serif">OECD (2012), <em>Test No. 211: Daphnia magna Reproduction Test</em>, OECD Guidelines for the Testing of Chemicals, Section 2, OECD Publishing, Paris, <a href="https://doi.org/10.1787/9789264185203-en" title="">https://doi.org/10.1787/9789264185203-en</a>.</span></span></p>
<p><span style="font-size:14px"><span style="font-family:Arial,Helvetica,sans-serif">Tellam RL, Vuocolo T, Johnson SE, Jarmey J, Pearson RD. 2000. Insect chitin synthase. cDNA sequence, gene organization and expression. Eur J Biochem. 267(19):6025–6043. doi:10.1046/j.1432-1327.2000.01679.x.</span></span></p>
<p><span style="font-size:14px"><span style="font-family:Arial,Helvetica,sans-serif">Wang, Z.; Yang, H.; Zhou, C.; Yang, W. J.; Jin, D. C.; Long, G. Y. Molecular Cloning, Expression, and Functional Analysis of the Chitin Synthase 1 Gene and Its Two Alternative Splicing Variants in the White-Backed Planthopper, Sogatella Furcifera (Hemiptera: Delphacidae). Sci. Rep. 2019, 9 (1), 1–14. https://doi.org/10.1038/s41598-018-37488-5.</span></span></p>
2018-05-24T15:58:58
2021-02-17T05:30:13
Increase, Mortality
Increase, Mortality
Individual
<p><span style="font-size:14px">This key event is observed at the biological level of the individual and describes the increase of mortality of individuals upon exposure to a stressor.</span></p>
<p><span style="font-size:14px">The AO can be detected by observation, for example by immobilization of the respective organisms. There exist guidelines for the characterization of this AO in arthropods. For example, the OECD 202 Daphnia sp. Acute immobilization test </span><!--[if supportFields]><span lang=EN-US
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yes'></span>ADDIN CSL_CITATION
{"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1787/9789264069947-en","ISBN":"9789264069947","PMID":"128","abstract":"This
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24 hours at the start of the test, are exposed to the test substance at a range
of concentrations (at least five concentrations) for a period of 48 hours.
Immobilisation is recorded at 24 hours and 48 hours and compared with control
values. The results are analysed in order to calculate the EC50 at 48h. Determination
of the EC50 at 24h is optional. At least 20 animals, preferably divided into
four groups of five animals each, should be used at each test concentration and
for the controls. At least 2 ml of test solution should be provided for each
animal (i.e. a volume of 10 ml for five daphnids per test vessel). The limit
test corresponds to one dose level of 100 mg/L. The study report should include
the observation for immobilized daphnids at 24 and 48 hours after the beginning
of the test and the measures of dissolved oxygen, pH, concentration of the test
substance, at the beginning and end of the
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style='mso-element:field-separator'></span></span><![endif]-->(OECD 2004)<!--[if supportFields]><span
lang=EN-US style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
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<p><span style="font-size:14px"><strong>Taxonomic: </strong>This AO is applicable to all living organisms.</span></p>
<p><span style="font-size:14px"><strong>Life stage: </strong>This AO is applicable to all life stages.</span></p>
<p><span style="font-size:14px"><strong>Sex: </strong>This AO is applicable to all sexes.</span></p>
<p><span style="font-size:14px"><strong>Chemical:</strong> Substances known to increase mortality in arthropods are of the family of pyrimidine nucleosides (e.g. polyoxin D and nikkomycin Z) (Gijswijt et al. 1979; Tellam et al. 2000; Arakawa et al. 2008).</span></p>
High
Unspecific
High
All life stages
High
High
<p><span style="font-size:14px">Arakawa T, Yukuhiro F, Noda H. 2008. Insecticidal effect of a fungicide containing polyoxin B on the larvae of <em>Bombyx mori</em> (Lepidoptera: Bombycidae), <em>Mamestra brassicae</em>, <em>Mythimna separata</em>, and <em>Spodoptera litura</em> (Lepidoptera: Noctuidae). Appl Entomol Zool. 43(2):173–181. doi:10.1303/aez.2008.173.</span></p>
<p><span style="font-size:14px">Gijswijt MJ, Deul DH, de Jong BJ. 1979. Inhibition of chitin synthesis by benzoyl-phenylurea insecticides, III. Similarity in action in <em>Pieris brassicae</em> (L.) with Polyoxin D. Pestic Biochem Physiol. 12(1):87–94. doi:10.1016/0048-3575(79)90098-1.</span></p>
<p><span style="font-size:14px">OECD. 2004. Test No. 202: <em>Daphnia sp.</em> Acute Immobilisation Test. OECD OECD Guidelines for the Testing of Chemicals, Section 2. [accessed 2020 Mar 3]. https://www.oecd-ilibrary.org/environment/test-no-202-daphnia-sp-acute-immobilisation-test_9789264069947-en.</span></p>
<p><span style="font-size:14px">Tellam RL, Vuocolo T, Johnson SE, Jarmey J, Pearson RD. 2000. Insect chitin synthase. cDNA sequence, gene organization and expression. Eur J Biochem. 267(19):6025–6043. doi:10.1046/j.1432-1327.2000.01679.x.</span></p>
2016-11-29T18:41:24
2020-10-26T05:18:16
ac34a1e4-51f3-485c-8aaa-e0ba4bf5ac85
b2a754b7-cd59-4cc2-93dc-b1c282c044fd
<p><span style="font-size:14px">Chitin in the arthropod cuticle is synthesized by the chitin synthase isoform 1 (CHS-1) which spans the plasma membrane on the apical plasma membrane of epithelial cells (Locke and Huie 1979; Binnington 1985; Merzendorfer and Zimoch 2003; Merzendorfer 2006). Since CHS-1 is the enzyme to polymerize chitin from UDP-<em>N</em>-Acetylglucosamine (UDP-GlcNAc) (Merzendorfer 2006), it is solely responsible for the content of chitin in the exoskeleton. Consequently, the inhibition of CHS-1 leads to a decrease in chitin content in the arthropod cuticle.</span></p>
<p><span style="font-size:14px">The process of chitin synthesis in arthropods is well characterized. Although the exact mechanism of the polymerization reaction remains elusive, CHS-1 is known to be the key enzyme in the biosynthesis of chitin and therefore, responsible for the cuticular chitin content (Merzendorfer and Zimoch 2003; Merzendorfer 2006). Therefore, the biological plausibility of this KER can be regarded as high.</span></p>
<p><span style="font-size:14px">Empirical evidence for the occurrence of both KEs, the inhibition of CHS-1 and the decrease in cuticular chitin content exist. For example, the occurrence of chitin synthase inhibition was characterized using cell free crude enzyme preparations <em>in vitro </em>from coleopteran, lepidopteran and dipteran insect species upon treatment with polyoxin B, polyoxin D and nikkomycin Z (Cohen and Casida 1982; Kuwano and Cohen 1984; Cohen and Casida 1990; Zhang and Yan Zhu 2013). The cuticular chitin content was characterized <em>in vivo</em> in <em>Artemia salina </em>or using cultured integumental tissue from lepidopteran and dipteran species after exposure to polyoxin D and nikkomycin Z as well as the phthalimides captan, captafol, and folpet (Gijswijt et al. 1979; Turnbull and Howells 1982; Calcott and Fatig 1984; Gelman and Borkovec 1986; Zhuo et al. 2014). Data from studies with specific stressors assessing both endpoints and therefore supporting dose concordance of the KER are lacking. However, results from studies where CHS-1 was knocked down by RNA interference support temporal concordance of the KER (Arakane et al. 2005, Li et al. 2017, Zhang X. et al. 2010). Given the support for temporal concordance and the lack of studies showing dose concordance, the empirical evidence for this KER was judged as moderate.</span></p>
<p><span style="font-size:14px">The major uncertainty in this KER is the absence of studies which assess both endpoints, the inhibition of the chitin synthase and the decrease in cuticular chitin content after exposure to specific stressors.</span></p>
Moderate
Unspecific
High
Larvae
High
Juvenile
Moderate
Adult
Moderate
Moderate
<p><span style="font-size:14px"><strong>Taxonomic: </strong>Likely, this KER is likely applicable to the whole phylum of arthropods as they all depend on the synthesis of chitin.</span></p>
<p><span style="font-size:14px"><strong>Life stage: </strong>This KER is applicable for organisms synthesizing chitin in order to grow and develop, namely larval stages of insects and all life stages of crustaceans and arachnids.</span></p>
<p><span style="font-size:14px"><strong>Sex: </strong>This KER is applicable to all sexes.</span></p>
<p><span style="font-size:14px"><strong>Chemical: </strong>Substances inducing both, the inhibition of CHS-1 and the decrease in cuticular chitin content are of the family of pyrimidine nucleosides (e.g. polyoxin D, polyoxin B and nikkomycin Z) (Gijswijt et al. 1979; Cohen and Casida 1982; Turnbull and Howells 1982; Calcott and Fatig 1984; Kuwano and Cohen 1984; Cohen and Casida 1990; Zhang and Yan Zhu 2013; Zhuo et al. 2014; Osada 2019). The phthalimide captan was also shown to induce CHS-1 inhibition and a decrease in cuticular chitin content (Cohen and Casida 1982; Gelman and Borkovec 1986). However, studies assessing both endpoints in sequence are lacking.</span></p>
<p><span style="font-size:14px">Ampasala DR, Zheng S, Zhang D, Ladd T, Doucet D, Krell PJ, Retnakaran A, Feng Q. 2011. An epidermis-specific chitin synthase cDNA in Choristoneura fumiferana: Cloning, characterization, developmental and hormonal-regulated expression. Arch Insect Biochem Physiol. 76(2):83–96. doi:10.1002/arch.20404.</span></p>
<p><span style="font-size:14px">Arakane, Y.; Muthukrishnan, S.; Kramer, K. J.; Specht, C. A.; Tomoyasu, Y.; Lorenzen, M. D.; Kanost, M.; Beeman, R. W. The Tribolium Chitin Synthase Genes TcCHS1 and TcCHS2 Are Specialized for Synthesis of Epidermal Cuticle and Midgut Peritrophic Matrix. Insect Mol. Biol. 2005, 14 (5), 453–463. https://doi.org/10.1111/j.1365-2583.2005.00576.x.</span></p>
<p><span style="font-size:14px">Binnington KC. 1985. Ultrastructural changes in the cuticle of the sheep blowfly, <em>Lucilia</em>, induced by certain insecticides and biological inhibitors. Tissue Cell. 17(1):131–140. doi:10.1016/0040-8166(85)90021-7.</span></p>
<p><span style="font-size:14px">Braden L, Michaud D, Igboeli OO, Dondrup M, Hamre L, Dalvin S, Purcell SL, Kongshaug H, Eichner C, Nilsen F, et al. 2020. Identification of critical enzymes in the salmon louse chitin synthesis pathway as revealed by RNA interference-mediated abrogation of infectivity. Int J Parasitol. 50(10–11):873–889. doi:10.1016/j.ijpara.2020.06.007. https://doi.org/10.1016/j.ijpara.2020.06.007.</span></p>
<p><span style="font-size:14px">Calcott PH, Fatig RO. 1984. Inhibition of Chitin metabolism by Avermectin in susceptible Organisms. J Antibiot (Tokyo). 37(3):253–259. doi:10.7164/antibiotics.37.253.</span></p>
<p><span style="font-size:14px">Cohen E, Casida JE. 1982. Properties and inhibition of insect integumental chitin synthetase. Pestic Biochem Physiol. 17(3):301–306. doi:10.1016/0048-3575(82)90141-9.</span></p>
<p><span style="font-size:14px">Cohen E, Casida JE. 1990. Insect and Fungal Chitin Synthetase Activity: Specificity of Lectins as Enhancers and Nucleoside Peptides as Inhibitors. Pestic Biochem Physiol. 37(3):249–253. doi:10.1016/0048-3575(90)90131-K.</span></p>
<p><span style="font-size:14px">Gelman DB, Borkovec AB. 1986. The pharate adult clasper as a tool for measuring chitin synthesis and for identifying new chitin synthesis inhibitors. Comp Biochem Physiol Part C, Comp. 85(1):193–197. doi:10.1016/0742-8413(86)90073-3.</span></p>
<p><span style="font-size:14px">Gijswijt MJ, Deul DH, de Jong BJ. 1979. Inhibition of chitin synthesis by benzoyl-phenylurea insecticides, III. Similarity in action in <em>Pieris brassicae</em> (L.) with Polyoxin D. Pestic Biochem Physiol. 12(1):87–94. doi:10.1016/0048-3575(79)90098-1.</span></p>
<p><span style="font-size:14px">Kuwano E, Cohen E. 1984. The use of a <em>Tribolium</em> chitin synthetase assay in studying the effects of benzimidazoles with a terpene moiety and related compounds. Agric Biol Chem. 48(6):1617–1620. doi:10.1080/00021369.1984.10866362.</span></p>
<p><span style="font-size:14px">Li, T.; Chen, J.; Fan, X.; Chen, W.; Zhang, W. MicroRNA and DsRNA Targeting Chitin Synthase A Reveal a Great Potential for Pest Management of the Hemipteran Insect Nilaparvata Lugens. Pest Manag. Sci. 2017, 73 (7), 1529–1537. https://doi.org/10.1002/ps.4492.</span></p>
<p><span style="font-size:14px">Locke M, Huie P. 1979. Apolysis and the Turnover of Plasmamembrane Plaques during Cuticle formation in an Insect. Tissue Cell. 11(2):277–291. doi:10.1016/0040-8166(79)90042-9.</span></p>
<p><span style="font-size:14px">Merzendorfer H. 2006. Insect chitin synthases: A review. J Comp Physiol B Biochem Syst Environ Physiol. doi:10.1007/s00360-005-0005-3.</span></p>
<p><span style="font-size:14px">Merzendorfer H, Zimoch L. 2003. Chitin metabolism in insects: structure, function and regulation of chitin synthases and chitinases. J Exp Biol. 206(24):4393 LP – 4412. doi:10.1242/jeb.00709. http://jeb.biologists.org/content/206/24/4393.abstract.</span></p>
<p><span style="font-size:14px">Osada H. 2019. Discovery and applications of nucleoside antibiotics beyond polyoxin. J Antibiot (Tokyo). 72(12):855–864. doi:10.1038/s41429-019-0237-1. http://dx.doi.org/10.1038/s41429-019-0237-1.</span></p>
<p><span style="font-size:14px">Turnbull IF, Howells AJ. 1982. Effects of several larvicidal compounds on chitin biosynthesis by isolated larval integuments of the sheep blowfly <em>Lucilia cuprina</em>. Aust J Biol Sci. 35(5):491–504. doi:10.1071/BI9820491.</span></p>
<p><span style="font-size:14px">Wang Y, Fan HW, Huang HJ, Xue J, Wu WJ, Bao YY, Xu HJ, Zhu ZR, Cheng JA, Zhang CX. 2012. Chitin synthase 1 gene and its two alternative splicing variants from two sap-sucking insects, <em>Nilaparvata lugens</em> and <em>Laodelphax striatellus</em> (Hemiptera: Delphacidae). Insect Biochem Mol Biol. 42(9):637–646. doi:10.1016/j.ibmb.2012.04.009. http://dx.doi.org/10.1016/j.ibmb.2012.04.009.</span></p>
<p><span style="font-size:14px">Zhang, X.; Zhang, J.; Zhu, K. Y. Chitosan/Double-Stranded RNA Nanoparticle-Mediated RNA Interference to Silence Chitin Synthase Genes through Larval Feeding in the African Malaria Mosquito (Anopheles Gambiae). Insect Mol. Biol. 2010, 19 (5), 683–693. https://doi.org/10.1111/j.1365-2583.2010.01029.x.</span></p>
<p><span style="font-size:14px">Zhang X, Yan Zhu K. 2013. Biochemical characterization of chitin synthase activity and inhibition in the African malaria mosquito, <em>Anopheles gambiae</em>. Insect Sci. 20(2):158–166. doi:10.1111/j.1744-7917.2012.01568.x.</span></p>
<p><span style="font-size:14px">Zhuo W, Fang Y, Kong L, Li X, Sima Y, Xu S. 2014. Chitin synthase A: A novel epidermal development regulation gene in the larvae of <em>Bombyx mori</em>. Mol Biol Rep. 41(7):4177–4186. doi:10.1007/s11033-014-3288-1.</span></p>
2018-05-24T15:59:34
2021-02-17T07:50:29
b2a754b7-cd59-4cc2-93dc-b1c282c044fd
551997dc-7ff4-4fff-903d-be782c4e30eb
<p><span style="font-size:14px">As the arthropod cuticle is a central part in the molting process, its proper composition is indispensable for a proper molt. The ecdysis motor program, the behavioral part of ecdysis, constitutes a distinct motor pattern to split and shed the old cuticle <!--[if supportFields]><span lang=EN-US
style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA'><span style='mso-element:field-begin;mso-field-lock:
yes'></span>ADDIN CSL_CITATION
{"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1242/jeb.023879","ISSN":"00220949","PMID":"19181892","abstract":"A
possible role of the insect stomatogastric nervous system (STNS) in ecdysis was
first implied in early studies reporting on internal air pressure build-up in
the digestive tract and air swallowing during ecdysis. The frontal ganglion, a
major component of the insect STNS, was suggested to play an important part in
this behaviour. Recent neurophysiological studies have confirmed the critical
role of the STNS in the successful completion of both larval and adult moults
in insects. In aquatic arthropods, though much less studied, the STNS plays an
equally important and probably very similar role in water swallowing. Water
uptake is instrumental in splitting the crustacean cuticle and allowing
successful ecdysis. Current data are presented in a comparative view that
contributes to our understanding of the role of the STNS in arthropod
behaviour. It also sheds light on the question of homology of the STNS among
the different arthropod groups. New insights into the neurohormonal control of
ecdysis, related to the STNS in both insects and crustaceans, are also
presented and comparatively
discussed.","author":[{"dropping-particle":"","family":"Ayali","given":"Amir","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Journal
of Experimental
Biology","id":"ITEM-1","issue":"4","issued":{"date-parts":[["2009"]]},"page":"453-459","title":"The
role of the arthropod stomatogastric nervous system in moulting behaviour and
ecdysis","type":"article-journal","volume":"212"},"uris":["http://www.mendeley.com/documents/?uuid=636f3b9d-69cd-4358-8d2d-9451f22f3bf7"]}],"mendeley":{"formattedCitation":"(Ayali
2009)","plainTextFormattedCitation":"(Ayali
2009)","previouslyFormattedCitation":"(Ayali
2009)"},"properties":{"noteIndex":0},"schema":"https://github.com/citation-style-language/schema/raw/master/csl-citation.json"}<span
style='mso-element:field-separator'></span></span><![endif]-->(Ayali 2009)<!--[if supportFields]><span
lang=EN-US style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA'><span style='mso-element:field-end'></span></span><![endif]-->. As the cuticle supports muscular function <!--[if supportFields]><span
lang=EN-US style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
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mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA'><span style='mso-element:field-begin;mso-field-lock:
yes'></span>ADDIN CSL_CITATION
{"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1016/j.asd.2004.05.006","ISSN":"14678039","abstract":"Since
nearly all adult insects fly, the cuticle has to provide a very efficient and
lightweight skeleton. Information is available about the mechanical properties
of cuticle - Young's modulus of resilin is about 1 MPa, of soft cuticles about
1kPa to 50 MPa, of sclerotised cuticles 1-20 GPa; Vicker's Hardness of
sclerotised cuticle ranges between 25 and 80kgfmm-2; density is 1-1.3 kg m-3 -
and one of its components, chitin nanofibres, the Young's modulus of which is
more than 150 GPa. Experiments based on fracture mechanics have not been
performed although the layered structure probably provides some toughening. The
structural performance of wings and legs has been measured, but our
understanding of the importance of buckling is lacking: it can stiffen the
structure (by elastic postbuckling in wings, for example) or be a failure mode.
We know nothing of fatigue properties (yet, for instance, the insect wing must
undergo millions of cycles, flexing or buckling on each cycle). The remarkable mechanical
performance and efficiency of cuticle can be analysed and compared with those
of other materials using material property charts and material indices.
Presented in this paper are four: Young's modulus - density (stiffness per unit
weight), specific Young's modulus - specific strength (elastic hinges, elastic
energy storage per unit weight), toughness - Young's modulus (fracture
resistance under various loading conditions), and hardness (wear resistance).
In conjunction with a structural analysis of cuticle these charts help to
understand the relevance of microstructure (fibre orientation effects in
tendons, joints and sense organs, for example) and shape (including surface
structure) of this fibrous composite for a given function. With modern techniques
for analysis of structure and material, and emphasis on nanocomposites and
self-assembly, insect cuticle should be the archetype for composites at all
levels of scale. © 2004 Elsevier Ltd. All rights
reserved.","author":[{"dropping-particle":"","family":"Vincent","given":"Julian
F.V.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Wegst","given":"Ulrike
G.K.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Arthropod
Structure and
Development","id":"ITEM-1","issue":"3","issued":{"date-parts":[["2004"]]},"page":"187-199","title":"Design
and mechanical properties of insect
cuticle","type":"article-journal","volume":"33"},"uris":["http://www.mendeley.com/documents/?uuid=0a16940f-fa66-43c3-8dc5-a683f3a36ac4"]}],"mendeley":{"formattedCitation":"(Vincent
and Wegst 2004)","plainTextFormattedCitation":"(Vincent and
Wegst 2004)","previouslyFormattedCitation":"(Vincent and
Wegst
2004)"},"properties":{"noteIndex":0},"schema":"https://github.com/citation-style-language/schema/raw/master/csl-citation.json"}<span
style='mso-element:field-separator'></span></span><![endif]-->(Vincent and Wegst 2004)<!--[if supportFields]><span lang=EN-US
style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA'><span style='mso-element:field-end'></span></span><![endif]-->, it needs to possess a certain integrity in order to successfully molt. The integrity of the cuticle is also important after ecdysis as arthropods, such as insects and crustaceans, expand the new cuticle by swallowing air or water in order to build up pressure to split the old and expand the new exoskeleton and provide stability to the soft new cuticle <!--[if supportFields]><span
lang=EN-US style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA'><span style='mso-element:field-begin;mso-field-lock:
yes'></span>ADDIN CSL_CITATION
{"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.2307/1547867","ISSN":"0278-0372","author":[{"dropping-particle":"","family":"deFur","given":"Peter
L.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Mangum","given":"Charlotte
P.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"McMahon","given":"Brian
R.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Journal
of Crustacean
Biology","id":"ITEM-1","issue":"2","issued":{"date-parts":[["1985"]]},"page":"207-215","title":"Cardiovascular
and Ventilatory Changes During Ecdysis in the Blue Crab <i>Callinectes
Sapidus</i>
Rathbun","type":"article-journal","volume":"5"},"uris":["http://www.mendeley.com/documents/?uuid=5f9a7253-f58f-47c7-9979-dff8837e3df5"]},{"id":"ITEM-2","itemData":{"DOI":"10.1016/0022-0981(78)90074-6","ISSN":"00220981","abstract":"Water
ingestion at ecdysis by the western rock lobster. Panulirus longipes (Milne
Edwards) was investigated using the reference markers 51Cr-EDTA and 58Co-EDTA.
Two possible mechanisms controlling water absorption were examined: first,
changes in osmolarity of blood and muscle and secondly, the effects of extracts
of central nervous system. Water ingestion was 16.071 ± 2.365 ml kg-1 h-1
during swelling just before ecdysis (stage D4(S)) and 23.099 ± 1.238 ml kg-1
h-1 during stage A. There was no significant absorption in the foregut or
hindgut and the digestive gland appeared to be the site of major absorption.
Total water ingested during stages D4(S) and A was 13.7% of the proecdysis
weight. Calculating total water uptake by wet weight differences plus wet weight
of exuviae gave a value that was too high and instead weight increases were
calculated from a carapace length-weight formula. Allowing for postecdysis
increase in weight the net increase at ecdysis was 18.4-21.4% which was
4.7-7.7% more than the water ingested. It was concluded from this that water
enters the body at ecdysis both by ingestion and by absorption through the
external surface. It is suggested that water ingestion provides the main source
of swelling of the cephalothorax in stage D4(S) and after ecdysis both ingested
water and external absorption enables the flaccid abdomen and appendages to
swell rapidly. Statistically significant differences were found in the
concentrations of total cations and chloride in leg muscle during the
transition from stage C4 to late D4 but the trends were not consistent and
probably have no functional significance. There were no changes in the
concentration of osmotically active organic constituents. The freezing-point
depression of the blood in stage D4 was significantly higher than that in stage
C4(P < 0.02) but the mean difference was only 1.8%. It was concluded that
osmoticchanges were unlikely to be an important mechanism of water uptake.
Water-soluble extract (WSE) and acetone-soluble extract (ASE) of brains and
first ventral ganglia were without significant effect when compared together
with controls. There was a barely significant decrease, however, in water in
the proventriculus of WSE-treated animals compared with that of controls (P
< 0.05). and further investigation on the effects of such extracts on water
uptake at ecdysis is warranted. ©
1978.","author":[{"dropping-particle":"","family":"Dall","given":"W.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Smith","given":"D.
M.","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Press","given":"Biomedical","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Journal
of Experimental Marine Biology and
Ecology","id":"ITEM-2","issue":"1960","issued":{"date-parts":[["1978"]]},"title":"Water
uptake at ecdysis in the western rock lobster","type":"article-journal","volume":"35"},"uris":["http://www.mendeley.com/documents/?uuid=7de2ab94-c05e-4646-957b-a900dc162056"]},{"id":"ITEM-3","itemData":{"DOI":"10.1016/0022-1910(61)90090-7","ISSN":"00221910","abstract":"Two
methods of estimating insect blood volume are discussed. A method based on
haemocyte counts before and after injection of a measured volume of saline is
shown to be invalid, whereas a method based on the dilution of amaranth dye by
the haemolymph gave repeatable and consistent results. The blood volume of
Schistocerca gregaria Forsk. rises during the latter half of an instar, and
attains its highest level just prior to ecdysis. This high blood volume is
maintained for about 24 hr after ecdysis, then falls sharply to a mid-instar or
adult value, which is constant under the conditions described herein. The
increase in blood volume is shown to be due partly to changes in the
distribution of water within the body, and not merely to an intake of water
from the exterior. During periods of dietary water deficiency, the blood of the
desert locust can act as a reserve of water for other tissue requirements. ©
1961.","author":[{"dropping-particle":"","family":"Lee","given":"R.
M.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Journal
of Insect
Physiology","id":"ITEM-3","issue":"1","issued":{"date-parts":[["1961"]]},"page":"36-51","title":"The
variation of blood volume with age in the desert locust (<i>Schistocerca
gregaria</i>
Forsk.)","type":"article-journal","volume":"6"},"uris":["http://www.mendeley.com/documents/?uuid=7d2a6590-2216-4800-aee1-b3fb31ed55c7"]},{"id":"ITEM-4","itemData":{"DOI":"10.1111/j.1365-3032.1957.tb00361.x","ISSN":"13653032","author":[{"dropping-particle":"","family":"Clarke","given":"Kenneth
U.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Proceedings
of the Royal Entomological Society of London. Series A, General
Entomology","id":"ITEM-4","issue":"1-3","issued":{"date-parts":[["1957"]]},"page":"35-39","title":"On
the Increase in Linear Size During Growth in <i>Locusta
Migratoria</i>
L.","type":"article-journal","volume":"32"},"uris":["http://www.mendeley.com/documents/?uuid=eea788ce-c9d2-42b7-a36e-598377701670"]}],"mendeley":{"formattedCitation":"(Clarke
1957; Lee 1961; Dall et al. 1978; deFur et al. 1985)","plainTextFormattedCitation":"(Clarke
1957; Lee 1961; Dall et al. 1978; deFur et al.
1985)","previouslyFormattedCitation":"(Clarke 1957; Lee
1961; Dall et al. 1978; deFur et al.
1985)"},"properties":{"noteIndex":0},"schema":"https://github.com/citation-style-language/schema/raw/master/csl-citation.json"}<span
style='mso-element:field-separator'></span></span><![endif]-->(Clarke 1957; Lee 1961; Dall et al. 1978; deFur et al. 1985)<!--[if supportFields]><span
lang=EN-US style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA'><span style='mso-element:field-end'></span></span><![endif]-->. The arthropod cuticle mostly consists of chitin embedded in and crosslinked with a matrix of proteins <!--[if supportFields]><span
lang=EN-US style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA'><span style='mso-element:field-begin;mso-field-lock:
yes'></span>ADDIN CSL_CITATION
{"citationItems":[{"id":"ITEM-1","itemData":{"DOI":"10.1016/B978-0-12-384747-8.10007-8","ISBN":"9780123847478","abstract":"This
chapter highlights some of the recent and important findings obtained from
studies conducted on the synthesis, structure, physical state, modification,
organization, and degradation of chitin in insect tissues, as well as the
interplay of chitin with chitin-binding proteins, the regulation of genes
responsible for chitin metabolism, and, finally, the targeting of chitin metabolism
for insect-control purposes. Chitin is the major polysaccharide present in
insects and many other invertebrates as well as in several microbes, including
fungi. It serves as the skeletal polysaccharide of several animal phyla, such
as the Arthropoda, Annelida, Molluska, and Coelenterata. In several groups of
fungi, chitin replaces cellulose as the structural polysaccharide. In insects,
it is found in the body wall or cuticle, gut lining or peritrophic matrix (PM),
salivary gland, trachea, eggshells, and muscle attachment points. In the course
of evolution, insects have made excellent use of the rigidity and chemical
stability of the polymeric chitin to assemble both hard and soft extracellular
structures such as the cuticle (exoskeleton) and PM respectively, both of which
enable insects to be protected from the environment while allowing for growth,
mobility, respiration, and communication. All of these structures are primarily
composites of chitin fibers and proteins with varying degrees of hydration and trace
materials distributed along the structures. © 2012 Elsevier B.V. All rights
reserved.","author":[{"dropping-particle":"","family":"Muthukrishnan","given":"Subbaratnam","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Merzendorfer","given":"Hans","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Arakane","given":"Yasuyuki","non-dropping-particle":"","parse-names":false,"suffix":""},{"dropping-particle":"","family":"Kramer","given":"Karl
J.","non-dropping-particle":"","parse-names":false,"suffix":""}],"container-title":"Insect
Molecular Biology and Biochemistry","id":"ITEM-1","issued":{"date-parts":[["2012"]]},"number-of-pages":"193-235","publisher":"Elsevier
B.V.","title":"Chitin Metabolism in
Insects","type":"book"},"uris":["http://www.mendeley.com/documents/?uuid=24c204e2-9cb5-413f-81eb-5a90926cf1ed"]}],"mendeley":{"formattedCitation":"(Muthukrishnan
et al. 2012)","plainTextFormattedCitation":"(Muthukrishnan
et al. 2012)","previouslyFormattedCitation":"(Muthukrishnan
et al.
2012)"},"properties":{"noteIndex":0},"schema":"https://github.com/citation-style-language/schema/raw/master/csl-citation.json"}<span
style='mso-element:field-separator'></span></span><![endif]-->(Muthukrishnan et al. 2012)<!--[if supportFields]><span lang=EN-US
style='font-size:11.0pt;line-height:107%;font-family:"Calibri",sans-serif;
mso-ascii-theme-font:minor-latin;mso-fareast-font-family:Calibri;mso-fareast-theme-font:
minor-latin;mso-hansi-theme-font:minor-latin;mso-bidi-font-family:"Times New Roman";
mso-bidi-theme-font:minor-bidi;mso-ansi-language:EN-US;mso-fareast-language:
EN-US;mso-bidi-language:AR-SA'><span style='mso-element:field-end'></span></span><![endif]-->. If the chitin content is too low, the cuticle may not possess enough integrity to support muscular function or withstand the beforementioned stresses of ecdysis, which leads to the organism being stuck in the old cuticle or the rupture of the new cuticle.</span></p>
<p><span style="font-size:14px">The ecdysis motor program, the behavioral part of ecdysis, constitutes a distinct motor pattern to split and shed the old cuticle (Ayali 2009). As the cuticle supports muscular function (Vincent and Wegst 2004), it needs to possess a certain integrity in order to successfully molt. The integrity of the cuticle is also important after ecdysis as arthropods, such as insects and crustaceans, expand the new cuticle by swallowing air or water in order to build up pressure to expand the new exoskeleton and provide stability to the soft new cuticle (Clarke 1957; Lee 1961; Dall et al. 1978; deFur et al. 1985). The arthropod cuticle mostly consists of chitin embedded in and crosslinked with a matrix of proteins (Muthukrishnan et al. 2012). Given the well biological understanding of the processes, the biological plausibility can be regarded as high.</span></p>
<p><span style="font-size:14px">The cuticular chitin content was characterized <em>in vivo</em> in <em>Artemia salina </em>or using cultured integumental tissue from lepidopteran and dipteran insect species after exposure to polyoxin D and nikkomycin Z as well as the phthalimides captan, captafol, and folpet (Gijswijt et al. 1979; Turnbull and Howells 1982; Calcott and Fatig 1984; Gelman and Borkovec 1986; Zhuo et al. 2014). The event of premature molting was not assessed as endpoint in studies involving specific stressors rather than mentioned after exposure to polyoxin D, polyoxin B and nikkomycin Z (Gijswijt et al. 1979; Tellam et al. 2000; Arakawa et al. 2008). However, results from studies where CHS-1 was knocked down by RNA interference support temporal concordance of the KER (Arakane et al. 2005, Li et al. 2017, Zhang X. et al. 2010). Given the support for temporal concordance and the lack of studies showing dose concordance, the empirical evidence for this KER was judged as moderate.</span></p>
<p><span style="font-size:14px">The absence of studies (quantitatively) assessing premature molting constitutes a major data gap. A further data gap is the absence of studies which assess both, the decrease in cuticular chitin content and the increase in premature molting.</span></p>
Moderate
Unspecific
High
Larvae
High
Juvenile
Moderate
Adult
Moderate
Moderate
<p><span style="font-size:14px"><strong>Taxonomic: </strong>In all likelihood, this KER is applicable to the whole phylum of arthropods as they all depend on the synthesis of chitin and molting in order to develop.</span></p>
<p><span style="font-size:14px"><strong>Life stage: </strong>This KER is applicable for organisms synthesizing chitin and molting in order to grow and develop, namely larval stages of insects and all life stages of crustaceans and arachnids.</span></p>
<p><span style="font-size:14px"><strong>Sex: </strong>This KER is applicable to all sexes.</span></p>
<p><span style="font-size:14px"><strong>Chemical: </strong>Occurrence of a decrease in cticular chitin content as well as premature molting was observed after treatment with the pyrimidine nucleosides polyoxin D, polyoxin B and nikkomycin Z (Gijswijt et al. 1979; Turnbull and Howells 1982; Calcott and Fatig 1984; Gelman and Borkovec 1986; Tellam et al. 2000; Arakawa et al. 2008; Zhuo et al. 2014). However, studies causally linking both endpoints are lacking.</span></p>
<p><span style="font-size:14px">Arakane, Y.; Muthukrishnan, S.; Kramer, K. J.; Specht, C. A.; Tomoyasu, Y.; Lorenzen, M. D.; Kanost, M.; Beeman, R. W. The Tribolium Chitin Synthase Genes TcCHS1 and TcCHS2 Are Specialized for Synthesis of Epidermal Cuticle and Midgut Peritrophic Matrix. Insect Mol. Biol. 2005, 14 (5), 453–463. https://doi.org/10.1111/j.1365-2583.2005.00576.x.</span></p>
<p><span style="font-size:14px">Arakawa T, Yukuhiro F, Noda H. 2008. Insecticidal effect of a fungicide containing polyoxin B on the larvae of <em>Bombyx mori</em> (Lepidoptera: Bombycidae), <em>Mamestra brassicae</em>, <em>Mythimna separata</em>, and <em>Spodoptera litura</em> (Lepidoptera: Noctuidae). Appl Entomol Zool. 43(2):173–181. doi:10.1303/aez.2008.173.</span></p>
<p><span style="font-size:14px">Ayali A. 2009. The role of the arthropod stomatogastric nervous system in moulting behaviour and ecdysis. J Exp Biol. 212(4):453–459. doi:10.1242/jeb.023879.</span></p>
<p><span style="font-size:14px">Calcott PH, Fatig RO. 1984. Inhibition of Chitin metabolism by Avermectin in susceptible Organisms. J Antibiot (Tokyo). 37(3):253–259. doi:10.7164/antibiotics.37.253.</span></p>
<p><span style="font-size:14px">Clarke KU. 1957. On the Increase in Linear Size During Growth in <em>Locusta Migratoria</em> L. Proc R Entomol Soc London Ser A, Gen Entomol. 32(1–3):35–39. doi:10.1111/j.1365-3032.1957.tb00361.x.</span></p>
<p><span style="font-size:14px">Dall W, Smith DM, Press B. 1978. Water uptake at ecdysis in the western rock lobster. J Exp Mar Bio Ecol. 35(1960). doi:10.1016/0022-0981(78)90074-6.</span></p>
<p><span style="font-size:14px">deFur PL, Mangum CP, McMahon BR. 1985. Cardiovascular and Ventilatory Changes During Ecdysis in the Blue Crab <em>Callinectes Sapidus</em> Rathbun. J Crustac Biol. 5(2):207–215. doi:10.2307/1547867.</span></p>
<p><span style="font-size:14px">Gelman DB, Borkovec AB. 1986. The pharate adult clasper as a tool for measuring chitin synthesis and for identifying new chitin synthesis inhibitors. Comp Biochem Physiol Part C, Comp. 85(1):193–197. doi:10.1016/0742-8413(86)90073-3.</span></p>
<p><span style="font-size:14px">Gijswijt MJ, Deul DH, de Jong BJ. 1979. Inhibition of chitin synthesis by benzoyl-phenylurea insecticides, III. Similarity in action in <em>Pieris brassicae</em> (L.) with Polyoxin D. Pestic Biochem Physiol. 12(1):87–94. doi:10.1016/0048-3575(79)90098-1.</span></p>
<p><span style="font-size:14px">Lee RM. 1961. The variation of blood volume with age in the desert locust (<em>Schistocerca gregaria</em> Forsk.). J Insect Physiol. 6(1):36–51. doi:10.1016/0022-1910(61)90090-7.</span></p>
<p><span style="font-size:14px">Li, T.; Chen, J.; Fan, X.; Chen, W.; Zhang, W. MicroRNA and DsRNA Targeting Chitin Synthase A Reveal a Great Potential for Pest Management of the Hemipteran Insect Nilaparvata Lugens. Pest Manag. Sci. 2017, 73 (7), 1529–1537. https://doi.org/10.1002/ps.4492.</span></p>
<p><span style="font-size:14px">Muthukrishnan S, Merzendorfer H, Arakane Y, Kramer KJ. 2012. Chitin Metabolism in Insects. Elsevier B.V. http://dx.doi.org/10.1016/B978-0-12-384747-8.10007-8.</span></p>
<p><span style="font-size:14px">Tellam RL, Vuocolo T, Johnson SE, Jarmey J, Pearson RD. 2000. Insect chitin synthase. cDNA sequence, gene organization and expression. Eur J Biochem. 267(19):6025–6043. doi:10.1046/j.1432-1327.2000.01679.x.</span></p>
<p><span style="font-size:14px">Turnbull IF, Howells AJ. 1982. Effects of several larvicidal compounds on chitin biosynthesis by isolated larval integuments of the sheep blowfly <em>Lucilia cuprina</em>. Aust J Biol Sci. 35(5):491–504. doi:10.1071/BI9820491.</span></p>
<p><span style="font-size:14px">Vincent JFV, Wegst UGK. 2004. Design and mechanical properties of insect cuticle. Arthropod Struct Dev. 33(3):187–199. doi:10.1016/j.asd.2004.05.006.</span></p>
<p><span style="font-size:14px">Zhang, X.; Zhang, J.; Zhu, K. Y. Chitosan/Double-Stranded RNA Nanoparticle-Mediated RNA Interference to Silence Chitin Synthase Genes through Larval Feeding in the African Malaria Mosquito (Anopheles Gambiae). Insect Mol. Biol. 2010, 19 (5), 683–693. https://doi.org/10.1111/j.1365-2583.2010.01029.x.</span></p>
<p><span style="font-size:14px">Zhuo W, Fang Y, Kong L, Li X, Sima Y, Xu S. 2014. Chitin synthase A: A novel epidermal development regulation gene in the larvae of <em>Bombyx mori</em>. Mol Biol Rep. 41(7):4177–4186. doi:10.1007/s11033-014-3288-1.</span></p>
2018-05-24T15:59:48
2021-02-17T08:20:50
551997dc-7ff4-4fff-903d-be782c4e30eb
4f4b8697-fe71-4c3d-a088-43757bb0cb39
<p><span style="font-size:14px">During molting, arthropods pause food uptake and in certain cases also respiration (Camp et al. 2014; Song et al. 2017a). If molting is disrupted and the organism is not able to shed the old exoskeleton, the organism may eventually die of starvation, suffocation or the rupture of the exoskeleton.</span></p>
<p><span style="font-size:14px">In order to grow and develop, arthropods need to molt periodically (Heming 2018). Since molting is a determining point in arthropod development, the disruption of molting leads to increased mortality (Arakawa et al. 2008; Merzendorfer et al. 2012; Song et al. 2017a; Song et al. 2017b). During ecdysis, arthropods pause food intake and respiration (Camp et al. 2014; Song et al. 2017a). Therefore, if the molt cannot be completed, the organism may die of starvation or suffocation. Additionally, if the cuticle is immature, it may not withstand the stresses associated with ecdysis (Clarke 1957; Lee 1961; Dall et al. 1978; deFur et al. 1985), and the organism may die of desiccation or increased susceptibility to pathogens. Given the well understood biological processes, the biological plausibility of this KER was rated as high.</span></p>
<p><span style="font-size:14px">The event of premature molting is not well characterized. It gets mentioned as cause of death in studies with <em>Pieris brassicae, Spodoptera litura</em>, <em>Bombyx mori </em>and <em>Lucilia cuprina </em>after treatment with polyoxin D, polyoxin B, polyoxin AL (a mixture of polyoxins) and nikkomycin Z (Gijswijt et al. 1979; Tellam et al. 2000; Arakawa et al. 2008). The increase in mortality was reported in studies with <em>Lucilia cuprina</em>,<em> Spodoptera litura</em> and <em>Bombyx mori </em>(Tellam et al. 2000; Tellam and Eisemann 2000; Arakawa et al. 2008). Evidence from studies which assess and link both endpoints, and therefore would support dose concordance, is lacking. However, results from studies where CHS-1 was knocked down by RNA interference support temporal concordance of the KER (Arakane et al. 2005, Li et al. 2017, <span style="font-family:Calibri,sans-serif">Chen et al., 2008; Mohammed et al., 2017; Shang et al., 2016; Wang et al., 2012, 2019; Yang et al., 2013; Ye et al., 2019; Zhai et al., 2017; Zhang et al., 2010</span>). Given the support for temporal concordance and the lack of studies showing dose concordance, the empirical evidence for this KER was judged as moderate.</span></p>
<p><span style="font-size:14px">The absence of studies (quantitatively) assessing premature molting constitutes a major data gap. A further data gap is the absence of studies which assess both, increase in premature molting and the increase in mortality are lacking.</span></p>
Moderate
Unspecific
High
Larvae
Moderate
Juvenile
Moderate
Adult
Moderate
Moderate
<p><span style="font-size:14px"><strong>Taxonomic: </strong>Likely, this KER is applicable to the whole phylum of arthropods as they all depend on molting in order to develop.</span></p>
<p><span style="font-size:14px"><strong>Life stage: </strong>This KER is applicable for organisms molting in order to grow and develop, namely larval stages of insects and all life stages of crustaceans and arachnids.</span></p>
<p><span style="font-size:14px"><strong>Sex: </strong>This KER is applicable to all sexes.</span></p>
<p><span style="font-size:14px"><strong>Chemical: </strong>Occurrence of premature molting and an increase in mortality observed after treatment with the pyrimidine nucleosides ( e.g. polyoxin D, polyoxin B and nikkomycin Z) (Gijswijt et al. 1979; Tellam et al. 2000; Tellam and Eisemann 2000; Arakawa et al. 2008; New Zealand Environmental Protection Authority 2015). However, studies causally linking both endpoints are lacking.</span></p>
<p><span style="font-size:14px">Arakawa T, Yukuhiro F, Noda H. 2008. Insecticidal effect of a fungicide containing polyoxin B on the larvae of <em>Bombyx mori</em> (Lepidoptera: Bombycidae), <em>Mamestra brassicae</em>, <em>Mythimna separata</em>, and <em>Spodoptera litura</em> (Lepidoptera: Noctuidae). Appl Entomol Zool. 43(2):173–181. doi:10.1303/aez.2008.173.</span></p>
<p><span style="font-size:14px">Camp AA, Funk DH, Buchwalter DB. 2014. A stressful shortness of breath: Molting disrupts breathing in the mayfly <em>Cloeon dipterum</em>. Freshw Sci. 33(3):695–699. doi:10.1086/677899.</span></p>
<p><span style="font-size:14px">Chen, X.; Tian, H.; Zou, L.; Tang, B.; Hu, J.; Zhang, W. Disruption of Spodoptera Exigua Larval Development by Silencing Chitin Synthase Gene A with RNA Interference. Bull. Entomol. Res. 2008, 98 (6), 613–619. https://doi.org/10.1017/S0007485308005932.</span></p>
<p><span style="font-size:14px">Mohammed, A. M. A.; DIab, M. R.; Abdelsattar, M.; Khalil, S. M. S. Characterization and RNAi-Mediated Knockdown of Chitin Synthase A in the Potato Tuber Moth, Phthorimaea Operculella. Sci. Rep. 2017, 7 (1), 1–12. https://doi.org/10.1038/s41598-017-09858-y.</span></p>
<p><span style="font-size:14px">Clarke KU. 1957. On the Increase in Linear Size During Growth in <em>Locusta Migratoria</em> L. Proc R Entomol Soc London Ser A, Gen Entomol. 32(1–3):35–39. doi:10.1111/j.1365-3032.1957.tb00361.x.</span></p>
<p><span style="font-size:14px">Dall W, Smith DM, Press B. 1978. Water uptake at ecdysis in the western rock lobster. J Exp Mar Bio Ecol. 35(1960). doi:10.1016/0022-0981(78)90074-6.</span></p>
<p><span style="font-size:14px">deFur PL, Mangum CP, McMahon BR. 1985. Cardiovascular and Ventilatory Changes During Ecdysis in the Blue Crab <em>Callinectes Sapidus</em> Rathbun. J Crustac Biol. 5(2):207–215. doi:10.2307/1547867.</span></p>
<p><span style="font-size:14px">Gijswijt MJ, Deul DH, de Jong BJ. 1979. Inhibition of chitin synthesis by benzoyl-phenylurea insecticides, III. Similarity in action in <em>Pieris brassicae</em> (L.) with Polyoxin D. Pestic Biochem Physiol. 12(1):87–94. doi:10.1016/0048-3575(79)90098-1.</span></p>
<p><span style="font-size:14px">Heming BS. 2018. Insect development and evolution. Ithaca: Cornell University Press.</span></p>
<p><span style="font-size:14px">Lee RM. 1961. The variation of blood volume with age in the desert locust (<em>Schistocerca gregaria</em> Forsk.). J Insect Physiol. 6(1):36–51. doi:10.1016/0022-1910(61)90090-7.</span></p>
<p><span style="font-size:14px">Merzendorfer H, Kim HS, Chaudhari SS, Kumari M, Specht CA, Butcher S, Brown SJ, Robert Manak J, Beeman RW, Kramer KJ, et al. 2012. Genomic and proteomic studies on the effects of the insect growth regulator diflubenzuron in the model beetle species <em>Tribolium castaneum</em>. Insect Biochem Mol Biol. 42(4):264–276. doi:10.1016/j.ibmb.2011.12.008. http://dx.doi.org/10.1016/j.ibmb.2011.12.008.</span></p>
<p><span style="font-size:14px">New Zealand Environmental Protection Authority. 2015. Application for approval to import ESTEEM for release. https://www.epa.govt.nz/assets/FileAPI/hsno-ar/APP202334/fbce9a39e6/APP202334-APP202334-Staff-Report-Final-updated.pdf.</span></p>
<p><span style="font-size:14px">Shang, F.; Xiong, Y.; Xia, W. K.; Wei, D. D.; Wei, D.; Wang, J. J. Identification, Characterization and Functional Analysis of a Chitin Synthase Gene in the Brown Citrus Aphid, Toxoptera Citricida (Hemiptera, Aphididae). Insect Mol. Biol. 2016, 25 (4), 422–430. https://doi.org/10.1111/imb.12228.</span></p>
<p><span style="font-size:14px">Song Y, Evenseth LM, Iguchi T, Tollefsen KE. 2017b. Release of chitobiase as an indicator of potential molting disruption in juvenile <em>Daphnia magna</em> exposed to the ecdysone receptor agonist 20-hydroxyecdysone. J Toxicol Environ Heal - Part A Curr Issues. 80(16–18):954–962. doi:10.1080/15287394.2017.1352215. https://doi.org/10.1080/15287394.2017.1352215.</span></p>
<p><span style="font-size:14px">Song Y, Villeneuve DL, Toyota K, Iguchi T, Tollefsen KE. 2017a. Ecdysone Receptor Agonism Leading to Lethal Molting Disruption in Arthropods: Review and Adverse Outcome Pathway Development. Environ Sci Technol. 51(8):4142–4157. doi:10.1021/acs.est.7b00480.</span></p>
<p><span style="font-size:14px">Tellam RL, Eisemann C. 2000. Chitin is only a minor component of the peritrophic matrix from larvae of <em>Lucilia cuprina</em>. Insect Biochem Mol Biol. 30(12):1189–1201. doi:10.1016/S0965-1748(00)00097-7.</span></p>
<p><span style="font-size:14px">Tellam RL, Vuocolo T, Johnson SE, Jarmey J, Pearson RD. 2000. Insect chitin synthase. cDNA sequence, gene organization and expression. Eur J Biochem. 267(19):6025–6043. doi:10.1046/j.1432-1327.2000.01679.x.</span></p>
<p><span style="font-size:14px">Wang, Z.; Yang, H.; Zhou, C.; Yang, W. J.; Jin, D. C.; Long, G. Y. Molecular Cloning, Expression, and Functional Analysis of the Chitin Synthase 1 Gene and Its Two Alternative Splicing Variants in the White-Backed Planthopper, Sogatella Furcifera (Hemiptera: Delphacidae). Sci. Rep. 2019, 9 (1), 1–14. https://doi.org/10.1038/s41598-018-37488-5.</span></p>
<p><span style="font-size:14px">Wang, Y.; Fan, H. W.; Huang, H. J.; Xue, J.; Wu, W. J.; Bao, Y. Y.; Xu, H. J.; Zhu, Z. R.; Cheng, J. A.; Zhang, C. X. Chitin Synthase 1 Gene and Its Two Alternative Splicing Variants from Two Sap-Sucking Insects, Nilaparvata Lugens and Laodelphax Striatellus (Hemiptera: Delphacidae). Insect Biochem. Mol. Biol. 2012, 42 (9), 637–646. https://doi.org/10.1016/j.ibmb.2012.04.009.</span></p>
<p><span style="font-size:14px">Yang, W. J.; Xu, K. K.; Cong, L.; Wang, J. J. Identification, mRNA Expression, and Functional Analysis of Chitin Synthase 1 Gene and Its Two Alternative Splicing Variants in Oriental Fruit Fly, Bactrocera Dorsalis. Int. J. Biol. Sci. 2013, 9 (4), 331–342. https://doi.org/10.7150/ijbs.6022.</span></p>
<p><span style="font-size:14px">Ye, C.; Jiang, Y. Di; An, X.; Yang, L.; Shang, F.; Niu, J.; Wang, J. J. Effects of RNAi-Based Silencing of Chitin Synthase Gene on Moulting and Fecundity in Pea Aphids (Acyrthosiphon Pisum). Sci. Rep. 2019, 9 (1), 1–10. https://doi.org/10.1038/s41598-019-39837-4.</span></p>
<p><span style="font-size:14px">Zhai, Y.; Fan, X.; Yin, Z.; Yue, X.; Men, X.; Zheng, L.; Zhang, W. Identification and Functional Analysis of Chitin Synthase A in Oriental Armyworm, Mythimna Separata. Proteomics 2017, 17 (21), 1–11. https://doi.org/10.1002/pmic.201700165.</span></p>
<p><span style="font-size:14px">Zhang, J. et al. Silencing of two alternative splicing-derived mRNA variants of chitin synthase 1 gene by RNAi is lethal to the oriental migratory locust, Locusta migratoria manilensis (Meyen). Insect Biochem. Mol. Biol. 40, 824–833 (2010).</span></p>
2018-05-24T16:00:02
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Chitin synthase 1 inhibition leading to mortality
CHS-1 inhibition leading to mortality
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px">Simon Schmid <sup>1,2</sup>, You Song <sup>1</sup>, and Knut Erik Tollefsen <sup>1,2,3</sup></span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><sup>1</sup> Norwegian Institute for Water Research (NIVA), Section of Ecotoxicology and Risk Assessment, Økernveien 94, N-0579, Oslo, Norway</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><sup>2</sup> </span></span><span style="font-size:11.0pt"><span style="font-family:"Arial",sans-serif">Faculty of Environmental Science and Resource Management<span style="background-color:white"><span style="color:#212121"> (MINA)</span></span>, Norwegian University of Life Sciences (NMBU), N-1432, Ås, Norway</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><sup>3</sup> </span></span><span style="font-size:11.0pt"><span style="background-color:white"><span style="font-family:"Arial",sans-serif"><span style="color:#212121">Centre for Environmental Radioactivity (CERAD), Norwegian University of Life Sciences (NMBU), N-1432 Ås, Norway</span></span></span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px">Contact: Simon.Schmid@niva.no</span></span></p>
<p><u><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px">Acknowledgements:</span></span></u><br />
<span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><span style="background-color:white"><span style="color:black">This project has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Skłodowska-Curie grant agreement No 859891 and was supported by NIVA’s Computational Toxicology Program, NCTP (<a href="https://www.niva.no/en/projectweb/nctp" style="color:blue; text-decoration:underline">www.niva.no/nctp</a>).</span></span></span></span></p>
Open for citation & comment
WPHA/WNT Endorsed
Included in OECD Work Plan
1.94
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:11pt"><span style="font-size:10.5pt"><span style="background-color:white"><span style="color:#212529">In order to grow and develop, arthropods need to shed their exoskeleton (or cuticle) periodically and replace it with a new one in a process called molting. Successful molting, and therefore a successful development necessitates stability and integrity of the cuticle to support muscular contractions involved in the shedding of the old cuticle. The integrity of the cuticle is largely dependent on the <em>N</em>-acetylglucosamine (GlcNAc) polymer chitin. Therefore, arthropods heavily rely on chitin synthesis as chitin is one of the main constituents of the cuticle. The cuticular chitin synthase (CHS-1) is the key enzyme in the biosynthetic pathway and arthropods are therefore especially dependent on its proper function. The present AOP describes the effects of chemical inhibition of the cuticular chitin synthase (CHS-1) on the molting process leading to increased mortality in arthropods. Inhibition of CHS-1 is the molecular initiating event and leads to a decreased chitin content in the arthropod cuticle which leaves the organism immature at the stage for ecdysis. This phenomenon can be described as premature molting. The organism eventually dies due to being stuck in the old cuticle or due to the consequences of a weak exoskeleton after ecdysis. The AOP is considered to be very consistent. Essentiality of key events was rated as high for every key event and the biological plausibility was rated as high for the whole AOP. However, there does not exist very much empirical evidence that allows to draw a representative conclusion on dose concordance along the AOP whereas time concordance can be supported by knockdown studies of CHS-1. Therefore, empirical evidence was considered to be moderate and the quantitative understanding was considered to be low. The overall confidence in the AOP was valued as moderate. The present AOP will guide assay development for further experimental studies by revealing data and knowledge gaps. One of its primary applications will also be providing guidance in screening strategies in order to identify chemicals directly interacting with CHS-1.</span></span></span></span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px">Arthropods (including insects, crustaceans and arachnids) need to shed their exoskeleton in order to grow and reproduce. This process, also called molting or ecdysis, is mediated by behavioural mechanisms which involve the skeletal muscles (Ayali 2009; Song et al. 2017a). In order to properly shed its cuticle, the organism needs to possess a newly synthesized cuticle that possesses a certain integrity to support this process. Since chitin is a major constituent of the cuticle, it contributes substantially to its integrity (Cohen 2001; Vincent and Wegst 2004). Chitin is synthesized from uridine diphosphate-<em>N</em>-Acetylglucosamine (UDP-GlcNAc) in a polymerization reaction by the transmembrane enzyme chitin synthase isoform 1 (CHS-1). CHS-1 is localized on the apical side in the cuticular epithelium.<br />
Since chitin and the process of chitin synthesis does not occur in vertebrates, it can and has been exploited for the design of pest controlling agents. Inhibitors of chitin synthesis may not only be of use for the control of unwanted arthropods and fungi, they may also pose a risk for beneficial arthropods such as insects and crustaceans. Disruption of chitin synthesis or the endocrine mechanisms controlling molting generally lead to a disruption of ecdysis (Merzendorfer et al. 2012; Song et al. 2017a; Song et al. 2017b). If the amount of chitin in the cuticle decreases, the affected organism may not be able to molt properly and will most probably die of starvation or suffocation (Camp et al. 2014; Song et al. 2017a). Alternatively, if molting is completed despite an immature cuticle, the organism may be deformed and die as a consequence of a weak cuticle.</span><br />
<span style="font-size:14px">Therefore, the present AOP should build the basis of a mechanistic approach for the systematic evaluation and the risk assessment of chemicals interfering with chitin synthesis by directly inhibiting CHS-1.</span></span></p>
<p><span style="font-size:14px">Stressors known to competitively inhibit CHS1 are polyoxin B, polyoxin D and Nikkomycin Z (Cohen and Casida 1982; Cohen and Casida 1990; Zhang and Yan Zhu 2013). There may also be stressors that inhibit CHS-1 in a non-competitive manner which may become apparent in further characterization efforts of this MIE. There is also a study that reports inhibition of CHS-1 by the phthalimide fungicide captan (Cohen and Casida 1982). However, it remains elusive if the observed inhibition is due to specific interaction with the enzyme or due to unspecific protein binding which is the predominant mode of action of phthalimides (Lukens and Sisler 1958).</span></p>
<p><span style="font-size:14px">The Adverse Outcome is highly significant from a regulatory point of view. It is employed as regulatory endpoint in most studies assessing the toxicity of stressors.</span></p>
adjacent
Low
Moderate
adjacent
Low
Moderate
adjacent
Low
Moderate
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px">The essentiality of all key events was considered as high. Essentiality evaluations were mainly based on specifically designed studies demonstrating the expected effect pattern predicted by the AOP to occur after knockdown of CHS-1.</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><strong>Inhibition, Chitin synthase 1 (High): </strong>Knockdown of the cuticular chitin synthase leads to the expected pattern of effects described in this AOP. It decreases the cuticular chitin content and leads to premature molting associated mortality in insects (Arakane et al. 2005; X. Zhang et al. 2010; Li et al. 2017; Zhai et al. 2017)<strong>. </strong>If the cuticular chitin content was not directly measured as endpoint, knockdown of the CHS-1 led directly to the occurrence of premature molting associated increase of mortality (Chen et al. 2008; X. Zhang et al. 2010; Wang et al. 2012; Yang et al. 2013; Shang et al. 2016; Mohammed et al. 2017; Wang et al. 2019; Ye et al. 2019; Ullah et al. 2020)</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><strong>Decrease, Cuticular chitin content (High): </strong>Abolishment of the cuticular chitin synthesis through knockdown of CHS-1 leads to premature molting associated mortality (Arakane et al. 2005; X. Zhang et al. 2010; Li et al. 2017; Zhai et al. 2017). By knocking down the UDP-GlcNAc pyrophosphorylase (UAP), which catalyzes the last sugar conversion before the polymerization to chitin, it was shown that reduced chitin content leads to the same outcome as the knockdown of CHS-1. Namely premature molting and increased mortality (Arakane et al. 2011; Liu et al. 2013). Knockdown of trehalase genes, which constitutes the start of the chitin synthetic pathway and convert trehalose to glucose, leads to a similar pattern of effects, namely decreased cuticular chitin content and premature molting associated mortality (Chen et al. 2010; Shi et al. 2016).</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><strong>Increase, Premature molting (High): </strong>Several studies show that premature molting is a direct consequence of decreased chitin synthesis and leads to increased mortality. The KE is consistently listed as cause for mortality when CHS-1 is knocked down throughout a number of studies (Arakane et al. 2005; Chen et al. 2008; J. Zhang et al. 2010; X. Zhang et al. 2010; Wang et al. 2012; Yang et al. 2013; Shang et al. 2016; Li et al. 2017; Mohammed et al. 2017; Zhai et al. 2017; Wang et al. 2019; Ye et al. 2019).</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><strong><span style="font-size:14px">Increase, Mortality (High): </span></strong><span style="font-size:14px">Increased mortality was observed in all of the abovementioned studies.</span></span></p>
Moderate
Unspecific
High
Larvae
High
Juvenile
Moderate
Adult
High
High
High
High
High
High
High
High
High
High
High
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
Moderate
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><strong><span style="background-color:#ffffff">Taxonomic: </span></strong><span style="background-color:#ffffff">Since the whole phylum of arthropods is dependent on the synthesis of chitin to molt successfully, it is extremely likely that the AOP is applicable to all arthropods.</span><strong><span style="background-color:#ffffff"> </span></strong><span style="background-color:#ffffff">E</span>ffect data along the AOP exist from Dipteran, Lepidopteran and Coleopteran insect species as well as from Branchiopods and Anostracans of the crustacea. Although data is limited, KEs seem to be well conserved across taxa, as shown in available studies with specific stressors known to inhibit CHS and in studies where CHS-1 was knocked down by RNA interference. However, due to limited data availability, it was not possible to cover whole taxa but rather single species in the assessment of KEs. Alignment of amino acid residues in the catalytic center of CHS-1 using the Sequence Alignment to Predict Across Species Susceptibility tool (SeqAPASS, <a href="https://seqapass.epa.gov/seqapass/info.xhtml">https://seqapass.epa.gov/seqapass</a>, </span></span><span style="font-size:14px"><span style="font-family:"Arial",sans-serif">LaLone et al. 2016</span></span><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px">), confirmed structural and functional conservation in various insect, arachnid and crustacean species, strenghtening the evidence for the applicability domain to be the whole phylum of arthropods. However, taxonomic applicability may not only be defined by structural conservation of the protein sequence. So the evidence for the taxonomic applicability for species with support only from sequence alignment was judged as moderate, whereas evidence for species with support from sequence alignment and effect data was judged as high.</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><strong>Life stage: </strong>The AOP is applicable for organisms undergoing continuous molt cycles. As insects do not molt in their adulthood, the AOP is only applicable for larval and pupal stages of insects. Crustaceans and arachnids grow and molt throughout their lifetime (Passano 1961; Uhl et al. 2015), which makes the AOP applicable to all life stages, where juvenile life stages might be more susceptible to chemical perturbations due to higher growth rate and therefore more frequent molting.</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><strong>Sex: </strong>The AOP is applicable to all sexes.</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><strong>Chemical: </strong>Substances known to trigger the MIE and leading to the AO are of the family of pyrimidine nucleosides (e.g. polyoxin D, polyoxin B and nikkomycin Z) (Osada 2019). There also exists evidence for phthalimides (captan, captafol and folpet) to inhibit CHS-1 activity and to decrease the cuticular chitin content <em>in vitro</em> (Cohen and Casida 1982; Gelman and Borkovec 1986). However, as these substances are known to covalently bind to thiol groups in proteins (Lukens and Sisler 1958), it is not clear if the inhibition is due to specific CHS-1 inhibition or due to unspecific protein binding.</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px">The essentiality of all key events was considered as high. Essentiality evaluations were mainly based on specifically designed studies demonstrating the expected effect pattern predicted by the AOP to occur after knockdown of CHS-1.</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><strong>Inhibition, Chitin synthase 1 (High): </strong>Knockdown of the cuticular chitin synthase leads to the expected pattern of effects described in this AOP. It decreases the cuticular chitin content and leads to premature molting associated mortality in insects (Arakane et al. 2005; X. Zhang et al. 2010; Li et al. 2017; Zhai et al. 2017)<strong>. </strong>If the cuticular chitin content was not directly measured as endpoint, knockdown of the CHS-1 led directly to the occurrence of premature molting associated increase of mortality (Chen et al. 2008; X. Zhang et al. 2010; Wang et al. 2012; Yang et al. 2013; Shang et al. 2016; Mohammed et al. 2017; Wang et al. 2019; Ye et al. 2019; Ullah et al. 2020)</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><strong>Decrease, Cuticular chitin content (High): </strong>Abolishment of the cuticular chitin synthesis through knockdown of CHS-1 leads to premature molting associated mortality (Arakane et al. 2005; X. Zhang et al. 2010; Li et al. 2017; Zhai et al. 2017). By knocking down the UDP-GlcNAc pyrophosphorylase (UAP), which catalyzes the last sugar conversion before the polymerization to chitin, it was shown that reduced chitin content leads to the same outcome as the knockdown of CHS-1. Namely premature molting and increased mortality (Arakane et al. 2011; Liu et al. 2013). Knockdown of trehalase genes, which constitutes the start of the chitin synthetic pathway and convert trehalose to glucose, leads to a similar pattern of effects, namely decreased cuticular chitin content and premature molting associated mortality (Chen et al. 2010; Shi et al. 2016).</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><strong>Increase, Premature molting (High): </strong>Several studies show that premature molting is a direct consequence of decreased chitin synthesis and leads to increased mortality. The KE is consistently listed as cause for mortality when CHS-1 is knocked down throughout a number of studies (Arakane et al. 2005; Chen et al. 2008; J. Zhang et al. 2010; X. Zhang et al. 2010; Wang et al. 2012; Yang et al. 2013; Shang et al. 2016; Li et al. 2017; Mohammed et al. 2017; Zhai et al. 2017; Wang et al. 2019; Ye et al. 2019).</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><strong><span style="font-size:14px">Increase, Mortality (High): </span></strong><span style="font-size:14px">Increased mortality was observed in all of the abovementioned studies.</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px"><strong>Biological Plausibility: </strong>The biosynthesis of chitin is well characterized and is conserved among arthropods. Although the exact mode of action of chitin synthases remains elusive, it is widely accepted and well established that the chitin synthase is the key enzyme in the pathway, polymerizing chitin using UDP-<em>N</em>-Acetylglucosamine as substrate (Merzendorfer and Zimoch 2003).<br />
Arthropod cuticles mostly consist of chitin embedded into a matrix of cuticular proteins. It is therefore widely accepted that chitin contributes crucially to the quality and function of the cuticle (Reynolds 1987; Muthukrishnan et al. 2012). The molting process requires the new cuticle to be strong enough to withstand the stresses of ecdysis.<br />
During ecdysis, arthropods pause food intake and growth. If ecdysis is initiated before the new cuticle is strong enough, the organism likely dies of starvation or growth arrest (Song, Villeneuve, et al. 2017). It was also reported that certain arthropods pause respiration during ecdysis, which may lead to suffocation (Camp et al. 2014).<br />
Based on the well-established biological knowledge on the processes this AOP bases on, the biological plausibility for all KER was rated as high.</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:11pt"><strong><span style="font-size:10.5pt"><span style="background-color:white"><span style="color:#212529">Empirical Evidence: </span></span></span></strong><span style="font-size:10.5pt"><span style="background-color:white"><span style="color:#212529">Empirical evidence assessment was conducted on the basis of <em>in vitro </em>and <em>in vivo</em> experiments performed with stressors affecting key events throughout the AOP. Studies showed that the key events are affected by model stressors such as Polyoxin D and Nikkomycin Z, which are able to competitively inhibit CHS1 (Endo et al. 1970). Several studies provide evidence that polyoxin B, polyoxin D and nikkomycin Z trigger the MIE in cell free systems of coleopteran, lepidopteran and dipteran insect species<span style="font-size:10.5pt"><span style="background-color:white"><span style="color:#212529"> (Cohen 1982; Turnbull and Howells 1982; Kuwano and Cohen 1984; Cohen and Casida 1990; Zhang and Yan Zhu 2013). Also the cuticular chitin content was shown to be decreased by polyoxin D and nikkomycin Z </span></span></span>in lepidopteran and dipteran species as well as in the crustacean <em>Artemia salina</em><span style="font-size:10.5pt"><span style="background-color:white"><span style="color:#212529"> (Gijswijt et al. 1979; Calcott and Fatig 1984; Gelman and Borkovec 1986; Zhuo et al. 2014). The AO is supported by in vivo studies with polyoxin D and nikkomycin Z in dipteran insects and <em>Daphnia magna</em> (Tellam et al. 2000; Tellam and Eisemann 2000; Zhu et al. 2007; Zhang and Yan Zhu 2013; New Zealand Environmental Protection Authority 2015). A major data gap constitutes the absence of data covering the KE “Increase, premature molting”. This KE is mentioned in some studies but never assessed as an individual endpoint (Gijswijt et al. 1979; Tellam et al. 2000). Another major data gap is the lacking quantitative data for KERs. As endpoints were only measured as individual endpoints and not in sequence, it makes it nearly impossible to evaluate the dose for the KEs and KERs. However, data from studies where CHS-1 was knocked down are able to support temporal concordance for all KERs. Knockdown of CHS-1 led to decreased chitin content and subsequently to premature molting associated mortality (</span></span></span>Arakane et al., 2005; Li et al., 2017)<span style="font-size:10.5pt"><span style="background-color:white"><span style="color:#212529">. Based on the major data gaps and therefore the lacking information on dose concordance as well as the given time concordance, empirical evidence was evaluated to be moderate for the whole AOP.</span></span></span></span></span></span></span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><strong><span style="font-size:14px">Overall confidence in the AOP: </span></strong><span style="font-size:14px">Both, essentiality of KEs and the biological plausibility of the whole AOP were considered to be high. However, due to missing quantitative data and the lack of evidence for dose concordance, empirical evidence was judged to be moderate. Therefore the overall confidence in the AOP was evaluated as moderate.</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px">Quantitative data are limited for all KER and therefore the whole AOP. Therefore, predictions on the occurrence of downstream KE and the AO on the basis of the occurrence of upstream KEs is not readily feasible. Quantitative understanding of the AOP was therefore considered to be low.</span></span></p>
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px">Arthropods are responsible for many functions in terrestrial as well as aquatic ecosystems and are therefore jointly responsible for ecosystem health (Seastedt and Crossley 1984; Losey and Vaughan 2006; LeBlanc 2007). Therefore, it is important to develop AOPs which enhance the mechanistic knowledge on chemicals, such as chitin synthesis inhibitors, which may pose a risk to non-target arthropods. Those AOPs will contribute to the systematic use of mechanistic data to preserve beneficial arthropod populations and ecosystem health.<br />
The present AOP will help to guide future experimental studies by identifying data gaps. This will lead to the identification and development suitable bioassays in order to populate the AOP with (quantitative) experimental data which may allow for predictions of regulatory relevant endpoints on the basis of the occurrence of the MIE.<br />
The present AOP may also guide screening strategies in order to identify chemicals inhibiting CHS-1. The identified substances may then be prioritized and undergo a thorough hazard assessment.<br />
As there already exist approaches to assess mixture toxicity using the AOP framework (Altenburger et al. 2012; Beyer et al. 2014), the present AOP could be employed for the effect assessment of mixtures of chemicals that share the same KEs (e.g. AOP #361, <a href="https://aopwiki.org/aops/361">aopwiki.org/aops/361</a>, AOP #358, <a href="https://aopwiki.org/aops/358">aopwiki.org/aops/358</a>, and AOP #359, <a href="https://aopwiki.org/aops/359">aopwiki.org/aops/359</a>).</span></span></p>
High
High
High
Moderate
Moderate
Moderate
<p><span style="font-family:Arial,Helvetica,sans-serif"><span style="font-size:14px">Altenburger R, Scholz S, Schmitt-Jansen M, Busch W, Escher BI. 2012. Mixture toxicity revisited from a toxicogenomic perspective. Environ Sci Technol. 46(5):2508–2522. doi:10.1021/es2038036.</span></span></p>
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