《生命科学》 2011, 23(11): 1106-1113
摘 要：摘 要：油菜素内酯(brassinosteroids， BRs) 是一类重要的类固醇激素，参与调控植物生长发育的许多过程。结合应用遗传学、生物化学以及蛋白质组学等研究手段现已基本阐明了BR 信号转导的主要过程。BRI1 作为受体在细胞表面感知BR，BRI1 抑制子BKI1 从质膜上解离下来，使BRI1 与其共受体BAK1 结合。BRI1和BAK1 通过顺序磷酸化将BR 信号完全激活。活化的BRI1 将BSK 磷酸化激活，BSK 活化BSU1，BSU1将BIN2 去磷酸化使其失活，解除BIN2 对BES1/BZR1 的抑制功能。PP2A 可以将BES1/BZR1 去磷酸化激活，又可以将受体BRI1 去磷酸化促使其降解。BR信号的传递最终使去磷酸化状态的BES1/BZR1 在细胞内累积，激活BR 信号通路下游的转录调控。
关键词：油菜素内酯；受体激酶；信号转导；BRI1 ；BAK1
Abstract: Abstract: Brassinosteroids (BRs) are a class of steroidal hormones， playing essential roles in a wide range of processes during plant growth and development. The combined genetics， biochemistry and proteomics approaches have been employed to elucidate the major events in BR signaling pathway， mainly via a series of reversible phosphorylation and dephosphorylation processes. Perception of BR by the BR receptor BRI1 at cell surface leads to the dissociation of BRI1 kinase inhibitor BKI1 from the plasma membrane and association of BRI1 with its coreceptor BAK1. Sequential transphosphorylation of the paired BRI1/BAK1 receptor kinases completely activates the BR signaling cascade. BRI1 phosphorylation of the BSK kinases leads to the activation of the BSU1 phosphatases， which can function to dephosphorylate and inactivate the BIN2 kinase. PP2A phosphatases play dual roles in mediating BR signaling pathway including dephosphorylating BES1/BZR1 transcription factors to promote their functions and dephosphorylating BRI1 to make it less stable. These events result in the accumulation of unphosphorylated BES1/BZR1 transcription factors in the nucleus and subsequent activation of the downstream transcriptional network.
Key words: brassinosteroids; receptor kinase; signal transduction; BRI1; BAK1
