A WUSCHEL-related homeobox transcription factor orchestrates a transcriptional cascade to regulates fruit ripening in tomato

Fruit ripening is a complex, genetically programmed process involving the action of critical transcription factors (TFs). Despite the established significance of WUSCHEL-related homeobox (WOX) TFs in plant development, the involvement of WOXs and the associated regulatory network in fruit ripening regulation remain enigmatic.Here, we found that overexpression of SlWOX13 accelerated fruit ripening, whereas knockout SlWOX13 delayed this process. Moreover, ethylene synthesis and carotenoids accumulation were significantly inhibited in slwox13 mutant fruit, while accelerated in SlWOX13 overexpression fruit. Integrated analyses of RNA-seq and ChIP-seq identified 546 direct targets of SlWOX13, among which 345 were negatively regulated by SlWOX13 and 201 were positively regulated. Biochemical analyses demonstrated that SlWOX13 directly binds to the promoter of ACO1, ETR4, EIL1, ERF.B3, Psy1, PDS, and BCH, activating its transcriptional expression, thereby promoting ethylene synthesis, signaling and carotenoids biosynthesis in tomato fruits. Furthermore, SlWOX13 directly regulated the expression of ripening-related TFs including RIN, NAC4, and NOR. Consequently, these contributed to promote fruit ripening. In conclusion, we identified a homeobox transcription factor SlWOX13 as a control element of fruit ripening in tomato. SlWOX13 orchestrates a regulatory cascade that involves transcriptional activation of RIN, NAC4, and NOR, key transcription factors activation ripening related-gens and thus promotes fruit ripening, and transcriptional activation of ethylene synthesis(ACO1), receptor (ETR4), signaling(EIL1 and ERF.B3), and carotenoids biosynthesis(Psy1, PDS, and BCH) genes involved in fruit ripening.