Tomato Transcription Factor SlWUS Plays an Important Role in Tomato Flower and Locule Development

Abstract

Tomato is a model species for fleshy fruit development. The shapes and sizes of tomato (<i>Solanum lycopersicum L.</i>) are mainly controlled by several loci, including locule number (<i>lc</i>). Two single nucleotide polymorphisms were found downstream of <i>WUSCHEL</i> (<i>SlWUS</i>) in a putative tomato CArG <i>cis</i>-regulatory element. The <i>lc</i> mutation may affect the binding of <i>AGAMOUS</i>(<i>AG</i>), cause the up-regulation of <i>SlWUS</i> and result in increased locule numbers. In this study, tissue expression levels showed that <i>SlWUS</i> is expressed in young floral buds and shoot apexes. Silencing <i>SlWUS</i> on an <i>lc</i> mutant genetic background with an RNA interference (RNAi) strategy resulted in smaller flowers and fruit than those of the wild-type plants, with decreased locule number. Further study revealed that the <i>SlWUS</i> RNAi lines exhibited altered expression levels of the <i>TAG1</i> and <i>SlCLV3</i> genes that participate in the regulation of tomato flower and fruit locule development. In conclusion, this study provides the first genetic evidence that <i>SlWUS</i> may be the candidate gene of the <i>lc</i> locus and reveals the function of <i>SlWUS</i> in flower development.