# Discovering protein degradation mechanisms that regulate the plant circadian clock

> **NIH NIH R35** · YALE UNIVERSITY · 2022 · $418,750

## Abstract

Project Summary/Abstract
The circadian clock is necessary to synchronize biological processes with the environment. A properly timed
clock relies on rapid creation and destruction of clock proteins. Despite this, few protein degradation
mechanisms have been discovered that regulate the circadian clock of plants. This is likely due to genetic
redundancy amongst the E3 ubiquitin ligases that control protein ubiquitylation. Arabidopsis has served as a
powerful system for discovering molecular components of the circadian clock using live imaging for forward
and reverse genetic screens. My laboratory has leveraged these advantages to perform two reverse genetic
screens of E3 ubiquitin ligase families, overcoming traditional problems with genetic redundancy and
identifying a host of new regulators of circadian clock function. This proposal describes the design and
execution of this screen and the early functional characterization of newly discovered clock regulators.
Functional characterization relies on our streamlined workflow that allows us to rapidly determine the E3
ubiquitin ligase substrate proteins, validate these potential substrates, and perform genetic and biochemical
experiments demonstrating their role in clock function. The proposal then describes our two main laboratory
goals moving forward: 1) completion of the proposed screens and 2) functional characterization of the newly
discovered clock regulators. These studies will determine how protein degradation mechanisms can help
clocks sense external signals, maintain a 24 hour rhythm, and connect to downstream rhythmic biological
processes.
The circadian clock regulates fundamental biological processes including photosynthesis, metabolism,
defense, and growth. Thus, the work that we perform will have far-reaching impacts because: 1) it will provide
the basic molecular building blocks that are necessary to generate a robust 24 hour clock in plants, 2) it will
serve as a framework for similar studies in non-plant systems, and 3) it will provide a more comprehensive
understanding of the post-translational mechanisms that overlay transcriptional feedback loops of clocks.
Successful completion of this proposal will reveal how post-translational degradation mechanisms can survey
cellular environments to control changes in transcriptional networks of circadian clocks and provide precise
timing to clock-controlled biological processes. In the longer term, this work will increase our understanding of
the regulation of critical biological processes in plants, but it will also translate to better understanding of clock
function and clock-related diseases in humans.

## Key facts

- **NIH application ID:** 10439765
- **Project number:** 5R35GM128670-05
- **Recipient organization:** YALE UNIVERSITY
- **Principal Investigator:** Joshua Martin Gendron
- **Activity code:** R35 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2022
- **Award amount:** $418,750
- **Award type:** 5
- **Project period:** 2018-07-19 → 2023-08-14

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10439765

## Citation

> US National Institutes of Health, RePORTER application 10439765, Discovering protein degradation mechanisms that regulate the plant circadian clock (5R35GM128670-05). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10439765. Licensed CC0.

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