API

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Relationship: 3863

Title

A descriptive phrase which clearly defines the two KEs being considered and the sequential relationship between them (i.e., which is upstream, and which is downstream). More help

PSII inhibition leads to Decreased PSII electron transport

Upstream event
The causing Key Event (KE) in a Key Event Relationship (KER). More help
PSII inhibition
Downstream event
The responding Key Event (KE) in a Key Event Relationship (KER). More help
Decreased PSII electron transport

Key Event Relationship Overview

The utility of AOPs for regulatory application is defined, to a large extent, by the confidence and precision with which they facilitate extrapolation of data measured at low levels of biological organisation to predicted outcomes at higher levels of organisation and the extent to which they can link biological effect measurements to their specific causes.Within the AOP framework, the predictive relationships that facilitate extrapolation are represented by the KERs. Consequently, the overall WoE for an AOP is a reflection in part, of the level of confidence in the underlying series of KERs it encompasses. Therefore, describing the KERs in an AOP involves assembling and organising the types of information and evidence that defines the scientific basis for inferring the probable change in, or state of, a downstream KE from the known or measured state of an upstream KE. More help

AOPs Referencing Relationship

AOP Name Adjacency Weight of Evidence Quantitative Understanding Point of Contact Author Status OECD Status
Atrazine-induced photosystem II inhibition leading to yield loss in rice (Oryza sativa) adjacent Moderate Low SURIYA S (send email) Under development: Not open for comment. Do not cite

Taxonomic Applicability

Latin or common names of a species or broader taxonomic grouping (e.g., class, order, family) that help to define the biological applicability domain of the KER.In general, this will be dictated by the more restrictive of the two KEs being linked together by the KER.  More help

Sex Applicability

An indication of the the relevant sex for this KER. More help

Life Stage Applicability

An indication of the the relevant life stage(s) for this KER.  More help

Key Event Relationship Description

Provides a concise overview of the information given below as well as addressing details that aren’t inherent in the description of the KEs themselves. More help

Inhibition of the photosystem II complex blocks the transfer of electrons from QA to QB, directly resulting in a decreased rate of electron transport through the photosystem II complex.

Evidence Collection Strategy

Include a description of the approach for identification and assembly of the evidence base for the KER. For evidence identification, include, for example, a description of the sources and dates of information consulted including expert knowledge, databases searched and associated search terms/strings.  Include also a description of study screening criteria and methodology, study quality assessment considerations, the data extraction strategy and links to any repositories/databases of relevant references.Tabular summaries and links to relevant supporting documentation are encouraged, wherever possible. More help

A literature search was conducted in PubMed and Google Scholar using keywords: "atrazine", "photosystem II", "D1 protein", and "electron transport". Studies measuring chlorophyll fluorescence (Fv/Fm) and oxygen evolution in isolated chloroplasts or whole leaves were prioritized.

Evidence Supporting this KER

Addresses the scientific evidence supporting KERs in an AOP setting the stage for overall assessment of the AOP. More help

Multiple studies demonstrate temporal and dose concordance. Binding of atrazine to the D1 protein occurs rapidly (within minutes), followed immediately by a measurable decrease in electron transport rate (ETR). The inhibition is dose-dependent, with higher concentrations of atrazine causing a near-complete block of electron flow from QA to QB.

Biological Plausibility
Addresses the biological rationale for a connection between KEupstream and KEdownstream.  This field can also incorporate additional mechanistic details that help inform the relationship between KEs, this is useful when it is not practical/pragmatic to represent these details as separate KEs due to the difficulty or relative infrequency with which it is likely to be measured.   More help

High. The structural and functional relationship between the D1 protein binding site and the electron transport chain is canonically established in plant physiology.

Uncertainties and Inconsistencies
Addresses inconsistencies or uncertainties in the relationship including the identification of experimental details that may explain apparent deviations from the expected patterns of concordance. More help

No significant inconsistencies in the core mechanism exist; the relationship is universally conserved across higher plants. Minor uncertainties may arise from differences in experimental conditions (e.g., light intensity, temperature) affecting baseline ETR values.

Known modulating factors

This table captures specific information on the MF, its properties, how it affects the KER and respective references.1.) What is the modulating factor? Name the factor for which solid evidence exists that it influences this KER. Examples: age, sex, genotype, diet 2.) Details of this modulating factor. Specify which features of this MF are relevant for this KER. Examples: a specific age range or a specific biological age (defined by...); a specific gene mutation or variant, a specific nutrient (deficit or surplus); a sex-specific homone; a certain threshold value (e.g. serum levels of a chemical above...) 3.) Description of how this modulating factor affects this KER. Describe the provable modification of the KER (also quantitatively, if known). Examples: increase or decrease of the magnitude of effect (by a factor of...); change of the time-course of the effect (onset delay by...); alteration of the probability of the effect; increase or decrease of the sensitivity of the downstream effect (by a factor of...) 4.) Provision of supporting scientific evidence for an effect of this MF on this KER. Give a list of references.  More help
Response-response Relationship
Provides sources of data that define the response-response relationships between the KEs.  More help

A sigmoidal dose-response curve describes the relationship, where increasing the concentration of bound atrazine leads to a proportional decrease in electron transport rate.

Time-scale
Information regarding the approximate time-scale of the changes in KEdownstream relative to changes in KEupstream (i.e., do effects on KEdownstream lag those on KEupstream by seconds, minutes, hours, or days?). More help

Rapid: Inhibition of electron transport occurs within seconds to minutes of exposure to atrazine.

Known Feedforward/Feedback loops influencing this KER
Define whether there are known positive or negative feedback mechanisms involved and what is understood about their time-course and homeostatic limits. More help

Domain of Applicability

A free-text section of the KER description that the developers can use to explain their rationale for the taxonomic, life stage, or sex applicability structured terms. More help

Taxonomic: Higher plants (Embryophyta), specifically Oryza sativa. Life Stage: All photosynthetic life stages. Sex: Not applicable.

References

List of the literature that was cited for this KER description. More help

1. Trebst, A. (2007). Inhibitors of photosystem II: Their history and mode of action. Zeitschrift für Naturforschung C, 62(3-4), 173-182.