Rice tillering, a key architecture trait determining grain yield, is highly regulated by a class of newly identified phytohormones, strigolactones (SLs). However, the whole SL signaling pathway from the receptor to downstream transcription factors to finally inhibit tillering remains unrevealed. In this study, we first found that brassinosteroids (BRs) strongly enhance tillering by promoting bud outgrowth in rice, which is largely different from the function of BRs in Arabidopsis. Genetic and biochemical analyses indicated that both the SL and BR signaling pathways control rice tillering by regulating the stability of D53 and/or the OsBZR1–RLA1–DLT module, a transcriptional complex in the rice BR signaling pathway. We further found that D53 interacts with OsBZR1 to inhibit the expression of FC1, a local inhibitor of tillering, and that this inhibition depends on direct DNA binding by OsBZR1, which recruits D53 to the FC1 promoter in rice buds. Taken together, these findings uncover a mechanism illustrating how SLs and BRs coordinately regulate rice tillering via the early responsive gene FC1.

水稻分till是决定谷物产量的关键结构特征，它受到一类新近鉴定的植物激素，松果内酯（SLs）的高度调控。然而，从受体到下游转录因子以最终抑制分er的整个SL信号传导途径仍未揭示。在这项研究中，我们首先发现油菜素内酯类固醇（BRs）通过促进水稻中的芽长出而显着增强分till，这与拟南芥中BRs的功能有很大不同。遗传和生化分析表明，SL和BR信号通路均通过调节D53和/或水稻BR信号通路中的转录复合物OsBZR1-RLA1-DLT模块的稳定性来控制水稻分till。我们进一步发现D53与OsBZR1相互作用以抑制FC1的表达，这是一种局部分of抑制剂，这种抑制作用取决于OsBZR1与DNA的直接结合，而OsBZR1将D53募集到水稻芽的FC1启动子上。综上所述，这些发现揭示了一种机制，阐明了SL和BR如何通过早期响应基因FC1协调调节水稻分till。