Brassinosteroid signaling integrates multiple pathways to release apical dominance in tomato

Significance For almost a century, auxin had been well-known as the master regulator of apical dominance. Recently, however, sugars were shown to be the initial regulator of apical dominance, while strigolactones (SLs) and cytokinins (CKs) act downstream of auxin to control bud outgrowth. However, the interactions of the different pathways have remained outstanding questions. Here, we report that brassinosteroids (BRs) are essential for the release of apical dominance in tomato. CK signaling relays information from auxin, SL, and sugars to promote the production of BRs, which activate the BZR1 transcription factor to suppress the expression of BRANCHED1 , an inhibitor of bud outgrowth. These findings demonstrate that hormonal and metabolic pathways impinge on a common BR signaling for controlling shoot branching.