# Genetic analysis of a developmental clock in Arabidopsis

> **NIH NIH R01** · UNIVERSITY OF PENNSYLVANIA · 2021 · $332,692

## Abstract

ABSTRACT
Developmental transitions are often depicted as highly buffered processes that lead from one
stereotypical state to a different stereotypical state. Changes in the relative timing of different
processes can have profound consequences for the viability of an organism and, on a longer
time scale, for the evolution of a species. The juvenile-to-adult transition in plants (vegetative
phase change) is an ideal system in which to study the mechanism and consequences of such
heterochronic variation. Compared to other developmental transitions in plants, vegetative
phase change is unusual in that it occurs relatively slowly and involves species-specific traits
that change gradually from leaf-to-leaf at slightly different rates. As a result, novel combinations
of traits are the rule, rather than the exception. This process is controlled by two closely-related
miRNAs, miR156 and miR157. miR156/157 are expressed at high levels early in shoot
development, but then decline dramatically, relieving the repression of their targets, SPL
transcription factors. We hypothesize the plasticity of vegetative phase change is attributable to
1) the functional differentiation of SPL genes; 2) the differential sensitivity of these genes to
miR156/157 and 3) natural variation in the level and/or expression pattern of miR156/miR157.
We will test this hypothesis in Arabidopsis thaliana by (Aim 1) characterizing the effect of loss-
of-function mutations in 6 key SPL genes on gene expression and leaf morphology. The
sensitivity of these genes to variation in the level of miR156/miR157 will be examined using
transgenic lines containing miR156-sensitive reporters. In Aim 2, we will characterize natural
variation in the expression pattern of miR156 and use QTL mapping to identify the genes
responsible for this variation. In Aim 3, we will perform a sensitized genetic screen to identify
mutations that increase the abundance of miR156 or interfere with its down-regulation, and will
determine the molecular identity of these mutations by whole genome sequencing of mutants in
segregating populations. In addition to contributing to an understanding of the molecular
mechanism and biological functions of vegetative phase change, these experiments address the
more general question of whether miRNA-mediated regulation of gene expression facilitates
developmental plasticity.

## Key facts

- **NIH application ID:** 10234652
- **Project number:** 2R01GM051893-24
- **Recipient organization:** UNIVERSITY OF PENNSYLVANIA
- **Principal Investigator:** Richard Scott Poethig
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $332,692
- **Award type:** 2
- **Project period:** 1995-01-01 → 2025-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10234652

## Citation

> US National Institutes of Health, RePORTER application 10234652, Genetic analysis of a developmental clock in Arabidopsis (2R01GM051893-24). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10234652. Licensed CC0.

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