# A Noncanonical Auxin-Sensing Mechanism Uncovered by Screening the Auxin Response Factor 3 Interacting Proteins in Tomato

## TL;DR

This study reveals a new auxin signaling mechanism in tomatoes involving SlARF3 and its interacting proteins, which influences fruit development.

## Contribution

The paper identifies a non-canonical auxin-sensing mechanism centered on SlARF3 in tomato development.

## Key findings

- SlARF3 interacts with 118 proteins, and these interactions are auxin-sensitive.
- An auxin-sensitive interaction between SlARF3 and TM29 was identified, linking to parthenocarpy.
- Silencing SlARF3 leads to parthenocarpic fruit formation in tomatoes.

## Abstract

Within the canonical auxin signaling pathway, Auxin Response Factors (ARFs) are transcriptionally repressed by AUX/IAA proteins under low auxin conditions, and this repression is alleviated as auxin concentrations increase. By contrast, ARF3 functions as a central regulator of gynoecium morphogenesis in Arabidopsis via a non-canonical auxin-sensing mechanism that relies on dose-dependent modulation of its protein–protein interaction network. To investigate whether an analogous regulatory mechanism operates in tomato (Solanum lycopersicum), we identified the tomato ARF3 homolog (SlARF3) and utilized it as bait in a yeast two-hybrid (Y2H) screen. This screening approach yielded 137 positive clones, corresponding to 118 putative interacting proteins. Notably, all of these interactions were abolished in the presence of 3-indoleacetic acid (IAA), indicating that SlARF3 engages in auxin-sensitive protein–protein interactions and thereby mediates auxin-dependent signal transduction. Among these, we identified an auxin-sensitive interaction between SlARF3 and TM29, a central regulator of parthenocarpy, underscoring its critical role in this developmental pathway. Functional analyses further demonstrated that silencing SlARF3 induces parthenocarpic fruit formation. Taken together, these findings define a previously uncharacterized SlARF3-centered interaction network and provide a conceptual framework for elucidating non-canonical auxin signaling pathways underlying tomato development.