ABSTRACTThe timing of flowering and inflorescence architecture are critical for the reproductive success of tomato, but the gene regulatory networks underlying these traits are still hardly explored. Here we show that the tomato FRUITFULL-like (FUL-like) genes FUL2 and MADS-BOX PROTEIN 20 (MBP20) induce flowering and repress inflorescence branching. FUL1 fulfils a less prominent role and appears to depend on FUL2 and MBP20 for its upregulation in the inflorescence meristem. Our results demonstrate that MBP10, the fourth tomato FUL-like gene, has probably lost its function. The tomato FUL-like proteins cannot homodimerize, but heterodimerize with JOINTLESS (J), SlMBP21 (J2), ENHANCER OF JOINTLESS (EJ2/MADS1) and the SOC1-homolog TOMATO MADS-box gene 3 (TM3), which are co-expressed during inflorescence meristem maturation. Transcriptome analysis revealed various interesting downstream targets, including five repressors of cytokinin signaling, which are all upregulated during the vegetative-to-reproductive transition in ful1/ful2/mbp10/mbp20 mutants. FUL2 and MBP20 can also bind in vitro to the upstream regions of these genes, thereby probably directly stimulating cell division in the meristem upon the transition to flowering. Our research reveals that the four tomato FUL-like genes have diverged functions, but together regulate the important developmental processes flowering time, inflorescence architecture and fruit development.
AGL23, a type I MADS-box gene that controls female gametophyte and embryo development in Arabidopsis
