# Compound Inflorescence (S) represses fruit growth and seed development in tomato

## TL;DR

This study shows that the S gene in tomatoes represses fruit and seed development, offering new insights into how fruit growth is regulated.

## Contribution

The study reveals a novel role of the WOX transcription factor S in repressing fruit and seed development through direct transcriptional repression of SlTEL1.

## Key findings

- Ectopic S expression reduces seed weight and suppresses fruit growth in tomatoes.
- The s-classic allele promotes fruit growth in small-fruited tomatoes but causes issues in large-fruited cultivars.
- S directly represses SlTEL1, a gene involved in fruit and seed development.

## Abstract

In most fruit-bearing plants, the growth and ripening of the fruit are highly coordinated with its seeds. In tomato (Solanum lycopersicum), fruit growth is regulated by a number of transcription factors. The WUSCHEL-RELATED HOMEOBOX (WOX) transcription factor COMPOUND INFLORESCENCE (S)/SlWOX9 is a key regulator of inflorescence branching and embryogenesis. In this study, we show that S activity is indispensable for fruit and seed development. Ectopic S expression led to a decrease in seed weight and markedly suppressed endoreduplication-associated fruit growth. Conversely, the s-classic allele promoted fruit growth in the small-fruited S. pimpinellifolium accession LA1781 though the promotion was offset by fruit overload and vegetative reversion of flowers in large-fruited cultivars. Through transcriptome profiling and DNA affinity purification sequencing (DAP-seq), we discovered that S targeted a set of genes involved in seed development. Moreover, we demonstrate that S regulates fruit and seed development mainly through direct transcriptional repression of the Mei2-like gene SlTEL1 (Solanum lycopersicum TERMINAL EAR-LIKE 1). These findings uncover a new aspect of transcription regulation of fruit growth and seed development by WOX transcription factors in tomato.

The online version contains supplementary material available at 10.1186/s43897-025-00183-x.