Tomato APETALA2 family member SlTOE1 regulates inflorescence branching by repressing SISTER OF TM3

Inflorescence architecture directly impacts yield potential in most crops. As a model of sympodial plants, tomato (Solanum lycopersicum) inflorescence exhibits highly structural plasticity. However, the genetic regulatory network of inflorescence architecture in tomato remains unclear. Here, we investigated a modulator of inflorescence branching in tomato, TARGET OF EAT1 (SlTOE1), an APETALA2 (AP2) family member found to be predominantly expressed in the floral meristem (FM) of tomato. sltoe1 knockout mutants displayed highly branched inflorescences and defective floral organs. Transcriptome analysis revealed that SISTER OF TM3 (STM3) and certain floral development-related genes were upregulated in the flower meristem of sltoe1. SlTOE1 could directly bind the promoters of STM3 and Tomato MADS-box gene 3 (TM3) to repress their transcription. Simultaneous mutation of STM3 and TM3 partially restored the inflorescence branching of the sltoe1cr mutants, suggesting that SlTOE1 regulates inflorescence development, at least in part through an SlTOE1STM3/TM3 module. Genetic analysis showed that SlTOE1 and ENHANCER OF JOINTLESS 2 (EJ2) additively regulate tomato inflorescence branching; their double mutants showed more extensive inflorescence branching. Our findings uncover a pathway controlling tomato inflorescence branching and offer deeper insight into the functions of AP2 subfamily members.