# Molecular mechanisms of auxin response in Arabidopsis

> **NIH NIH R01** · UNIVERSITY OF MINNESOTA · 2020 · $291,309

## Abstract

PROJECT SUMMARY
 Reversible serine/threonine phosphorylation of proteins plays an essential regulatory function in numerous
cellular processes. Type 2C protein phosphatases (PP2Cs) represent a major class of Ser/Thr phosphatases,
and defects in several human PP2Cs have been implicated in cancer, diabetes, heart disease, neural
disorders, and stress signaling. However, little is known about the mechanisms by which PP2C activity is
regulated. The plant hormone auxin regulates virtually every aspect of plant growth and development. Small
Auxin Up-RNA (SAUR) genes represent the largest class of auxin-induced genes. The SAUR19-24 subset of
highly related SAUR proteins specifically interact with and inhibit the enzymatic activity of PP2C.D family
phosphatases to promote cell expansion. In part, this involves SAUR proteins preventing PP2C.D-mediated
dephosphorylation of a key regulatory site of plasma membrane H+-ATPases. The long-term goal of this
project is to thoroughly understand the molecular mechanisms underlying auxin-mediated control of plant
growth and development. More specifically, the work outlined in this proposal will characterize and illuminate
the mechanism by which SAUR proteins regulate PP2C.D phosphatases to control auxin-mediated cell
expansion and other aspects of growth and development.
 The proposed studies include genetic, molecular, biochemical, and structural approaches to elucidate the
regulatory mechanisms by which SAURs control PP2C activity in the model plant Arabidopsis thaliana. This
plant provides a powerful genetic system for investigating conserved regulatory processes within multicellular
eukaryotes. PP2C.D functions will be revealed through both gain- and loss-of-function genetic analyses of saur
and pp2c.d mutant and transgenic lines, and the regulatory interactions between these two protein families
elucidated. Secondly, phosphoproteomic profiling experiments will be conducted to biochemically define
PP2C.D regulated pathways and identify potential phosphoprotein substrates important for auxin-mediated
growth. Lastly, the structure of a SAUR-PP2C.D complex will be determined and tested in biochemical and
genetic assays to illuminate the molecular mechanism of SAUR inhibition of PP2C.D activity at atomic
resolution. The findings from the proposed experiments will likely have direct parallels to the mechanisms
human cells employ to regulate PP2C activity, as PP2C structure and function are both highly conserved. Such
detailed understanding of PP2C regulatory mechanisms will facilitate the development of novel therapeutic
strategies to alter PP2C activity and combat disease. Further, as humans depend on plants for sources of
food, fiber, medicine and fuel, the proposed studies will elucidate plant growth control by the SAUR-PP2C.D
regulatory module and potentially lead to novel strategies for manipulating plant growth to benefit human
health.

## Key facts

- **NIH application ID:** 9858346
- **Project number:** 5R01GM067203-13
- **Recipient organization:** UNIVERSITY OF MINNESOTA
- **Principal Investigator:** WILLIAM M GRAY
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $291,309
- **Award type:** 5
- **Project period:** 2003-01-01 → 2022-02-28

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9858346

## Citation

> US National Institutes of Health, RePORTER application 9858346, Molecular mechanisms of auxin response in Arabidopsis (5R01GM067203-13). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/9858346. Licensed CC0.

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