Brassinosteroids (BRs) regulate a variety of physiological processes in plants via extensive crosstalk with diverse biological signaling networks. Although BRs are known to reciprocally regulate circadian oscillation, the molecular mechanism underlying BR-mediated regulation of circadian clock remains unknown. Here, we demonstrate that the BR-activated transcription factor bri1-EMS-SUPPRESSOR 1 (BES1) integrates BR signaling into the circadian network in Arabidopsis. BES1 repressed expression of CIRCADIAN CLOCK-ASSOCIATED 1 (CCA1) and LATE ELONGATED HYPOCOTYL (LHY) at night by binding to their promoters, together with TOPLESS (TPL). The repression of CCA1 and LHY by BR treatment, which occurred during the night, was compromised in bes1-ko and tpl-8 mutants. Consistently, long-term treatment with BR shortened the circadian period, and BR-induced rhythmic shortening was impaired in bes1-ko and tpl-8 single mutants and in the cca1-1lhy-21 double mutant. Overall, BR signaling is conveyed to the circadian oscillator via the BES1/TPL-CCA1/LHY module, contributing to gating diurnal BR responses in plants.

油菜素类固醇 (BR) 通过与多种生物信号网络的广泛串扰来调节植物中的多种生理过程。尽管已知 BR 可以相互调节昼夜节律振荡，但 BR 介导的生物钟调节的分子机制仍不清楚。在这里，我们证明了 BR 激活的转录因子bri1 -EMS-SUPPRESSOR 1 (BES1) 将 BR 信号整合到拟南芥的昼夜节律网络中。BES1通过与 TOPLESS (TPL) 结合到其启动子上，在夜间抑制昼夜节律时钟相关 1 ( CCA1 ) 和晚伸长下胚轴( LHY )的表达。BR 处理对CCA1和LHY的抑制发生在夜间，在bes1-ko和tpl-8突变体中受到损害。一致地，长期用 BR 治疗缩短了昼夜节律，并且 BR 诱导的节律性缩短在bes1-ko和tpl-8单突变体以及cca1-1lhy-21双突变体中受到损害。总体而言，BR 信号通过 BES1/TPL-CCA1/LHY 模块传递至昼夜节律振荡器，有助于控制植物的昼夜 BR 反应。