# Dual Regulatory Roles of SlGAMYB1 in Tomato Development: GA-Dependent and GA-Independent Mechanisms

## TL;DR

This study shows that SlGAMYB1 in tomatoes affects plant growth through both GA-dependent and GA-independent mechanisms, influencing size, leaf shape, and flower development.

## Contribution

The study reveals dual regulatory roles of SlGAMYB1 in tomato development via GA-dependent and independent pathways.

## Key findings

- Overexpression of SlGAMYB1m caused dwarfism due to reduced GA levels and altered GA metabolism gene expression.
- Leaf morphology changes were observed due to inhibited cell proliferation and altered epidermal cell size and number.
- Increased floral organ number was linked to upregulation of SlWUS, independent of GA signaling.

## Abstract

The R2R3-MYB transcription factor GAMYB plays crucial roles in plant growth and development, but the biological functions of SlGAMYB1 in tomato remain poorly understood. Here, we investigated the roles of SlGAMYB1 by overexpressing a miR159-resistant version (35S:SlGAMYB1m) in tomato. Transgenic plants exhibited a dwarf phenotype with reduced internode elongation, which was associated with decreased bioactive gibberellin (GA) levels due to transcriptional repression of SlGA3ox1 and activation of SlGA2ox1/2/4/5. Additionally, 35S:SlGAMYB1m altered leaf morphology by inhibiting cell proliferation through downregulation of cell cycle genes, resulting in larger but fewer epidermal cells. Intriguingly, 35S:SlGAMYB1m plants displayed increased floral organ number, a process likely mediated by the upregulation of SlWUS rather than GA signaling. These findings demonstrate that SlGAMYB1 regulates diverse aspects of tomato development through both GA-dependent and independent pathways, providing new insights into the functional diversification of GAMYB genes and potential strategies for genetic improvement of tomato architecture and yield.