The transcription factor SlDOF9 directly activates SlELP5 expression to regulate inflorescence length in tomato

Tomato inflorescence architecture is an important determinant of yield potential and fruit distribution, with inflorescence length and branching influencing resource allocation and harvestability. Although several regulators of inflorescence development have been identified, the genetic basis of natural variation in inflorescence length remains insufficiently characterized. Using a mapping population derived from LA1256 and Moneymaker, two lines with contrasting inflorescence lengths, we identify a quantitative trait locus, qIFL2.1, for inflorescence length on chromosome 2. Fine mapping and functional analyses identify SlELP5 as a strong candidate gene underlying qIFL2.1. Natural variation in the SlELP5 promoter is associated with altered SlELP5 expression, which is negatively correlated with inflorescence length. Consistently, SlELP5 overexpression in the LA1256 background reduces inflorescence length, supporting a negative role of SlELP5 in regulating this trait. Transcriptomic, dual-luciferase, and EMSA assays further show that SlDOF9 is upregulated in OE-SlELP5 lines and directly activates SlELP5 expression by binding to its promoter, supporting a SlDOF9-SlELP5 regulatory module. These findings provide insights into the molecular regulation of tomato inflorescence architecture and identify a potential target for precision breeding of inflorescence traits.