The SlTCP26 promoting lateral branches development in tomato.

KEY MESSAGE: The SlTCP26 negatively regulated auxin signal to relieve the apical dominance and suppressed abscisic acid signal to remove the lateral bud dormancy, promoting lateral branches development. Lateral branches formation from lateral buds is a complex regulatory process in higher plants, and the interaction between transcription factors and hormones is indispensable during this process. TCP transcription factors have been reported to regulate lateral branches development, while the detailed function, especially interacting with auxin and ABA during this process, was still ambiguous in tomato. In this study, a branch regulatory gene, SlTCP26, was identified in tomato, and its role along with its interaction to hormones during branch development, as investigated. The results indicated that overexpression of SlTCP26 would promote lateral branches development, and could suppress the expressing of the genes associated with IAA signaling, presenting similar effects in decapitated plants. Conversely, the exogenous IAA application could inhibit the expression of SlTCP26. Furthermore, the expressing of the ABA signaling-related genes was inhibited in SlTCP26 overexpressed tomato, similar to that in decapitated tomato. Our findings suggested that SlTCP26 may be a crucial adjuster for synergistic action between ABA and IAA signals during the development of lateral branches, and it could promote the lateral buds grow into lateral shoots, via inhibiting IAA signal to relieve the apical dominance and suppressing ABA signal to remove the lateral bud dormancy. Our study provided some insights for the development of tomato lateral branches to understand the apical dominance regulatory network.