# Mechanism of Auxin Action

> **NIH NIH R01** · UNIVERSITY OF CALIFORNIA, SAN DIEGO · 2020 · $99,890

## Abstract

Project Summary
 The plant hormone auxin is involved in virtually all aspects of plant growth and development. Over the
years we and others have demonstrated that auxin acts by stimulating the degradation of a family of
transcriptional repressors called the Aux/IAA proteins, through the action of the ubiquitin protein ligase
SCFTIR1/AFB. Although this basic pathway is well established, we still know very little about how auxin regulates
plant growth and development. Strikingly, auxin-regulated genes differ dramatically between cell types and
organs, consistent with the diverse roles of the hormone. The basis for this specificity is unknown. Similarly,
the activities of the Aux/IAA and ARF proteins are poorly characterized and the gene regulatory networks
(GRNs) that mediate various auxin-regulated growth processes have not been defined. Finally, we know little
about how auxin signaling is integrated with other environmental and genetic signaling pathways.
 Recently we discovered that one member of the TIR1/AFB family of auxin co-receptors, AFB1, has a key
role in a non-genomic rapid auxin response in the root. This was a surprising result because the TIR1/AFB
proteins are known to function in transcriptional regulation. We also demonstrated that AFB1 is highly
enriched in the cytoplasm and propose that it is this feature that leads to its specialized role in the rapid
response.
 In this proposal, we request funds to purchase a Keyence BZX 810 fluorescent microscope. This
instrument is ideally suited to assess the growth of Arabidopsis seedlings in real time. We have already
demonstrated its utility in studies of the role of auxin in rapid changes in root growth using an instrument at
the Salk Institute. We expect that the microscope will allow us to rapidly make progress in our understanding
of a novel and surprising function of the AFB1 protein

## Key facts

- **NIH application ID:** 10135618
- **Project number:** 3R01GM043644-31S1
- **Recipient organization:** UNIVERSITY OF CALIFORNIA, SAN DIEGO
- **Principal Investigator:** MARK A ESTELLE
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $99,890
- **Award type:** 3
- **Project period:** 1989-08-01 → 2023-01-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10135618

## Citation

> US National Institutes of Health, RePORTER application 10135618, Mechanism of Auxin Action (3R01GM043644-31S1). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10135618. Licensed CC0.

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