水稻转录因子OsWRKY53正向调控BR信号的分子机制研究

Rice plant architecture is closely related with grain yield, and Brassinosteroid (BR) is an important hormone regulating rice plant architecture. It is of great significance to investigate rice BR signaling network and the underlying regulation mechanism.. Our published studies have showed that the rice transcription factor OsWRKY53 is able to positively regulate BR signaling. However, the molecular mechanism of OsWRKY53 involved in BR signaling remains unclear.. The preliminary work of this application found that OsGSK2, a negative regulator of BR signaling, interacts with and phosphorylates OsWRKY53. In addition, OsWRKY53 interacts with OsBZR1, a positive regulator of BR signaling. Therefore, we hypothesize that OsWRKY53 acts downstream of OsGSK2 in the BR signaling pathway, and function synergistically with OsBZR1 to regulate downstream gene expression.. To verify this hypothesis, in this proposal, we will use a combination of biochemical, genetic, molecular and functional genomic approaches to study the molecular mechanism of OsWRKY53 involved in BR signaling. One is to analyze the molecular mechanism and biological significance of phosphorylation of OsWRKY53 by OsGSK2; the other is to explore the molecular mechanism of interaction between OsWRKY53 and OsBZR1.This proposal is expected to improve our understanding of rice BR signal network, and also provide potential target for breeding high yield cultivar.

水稻株型与产量密切相关，而油菜素内脂（BR）是调控水稻株型的重要激素。深入解析水稻BR信号网络及调控机理，对水稻株型育种具有重要意义。我们已发表的研究发现，水稻转录因子OsWRKY53是BR信号的正调控因子，但其正向调控BR信号的分子机制尚不清楚。本申请前期工作发现，BR信号负调控因子OsGSK2能够结合并磷酸化OsWRKY53；并且，OsWRKY53与BR信号正调控因子OsBZR1之间也存在互作关系。因此，推测OsWRKY53在BR信号通路中OsGSK2的下游，与OsBZR1相互作用共同调控下游相关基因的表达。为证实这个假说，本申请拟采用分子生物学、遗传学等多学科技术手段从两方面开展研究：一是解析OsGSK2磷酸化OsWRKY53的分子机制及生物学意义；二是探究OsWRKY53与OsBZR1协同调控BR信号的分子机理。本申请预期完善水稻BR信号网络，对株型育种具有重要的理论和应用价值。

在水稻（Oryza sativa）和其他植物中，株型和粒型与产量密切相关。油菜素类固醇(BR) 信号传导和丝裂原激活蛋白激酶 (MAPK) 途径 (OsMAPKKK10–OsMAPKK4–OsMAPK6) 是控制水稻株型和粒型的两个主要调节途径。然而，他们之间是否存在交流仍然不是很清楚。本项目发现OsWRKY53 介导了BR 信号传导和 MAPK 通路之间的交叉对话。生化和遗传分析表明 OsGSK2磷酸化 OsWRKY53并降低其蛋白稳定性，表明OsWRKY53是OsGSK2在BR信号传导中的底物。OsWRKY53与 OsBZR1相互作用；它们以一种平行的遗传学关系协同调控BR相关的发育过程。本项目还提供遗传证据发现OsWRKY53在叶角和粒型的调控上与OsMAPKKK10-OsMAPKK4-OsMAPK6级联反应在同一条途径上起作用，表明OsWRKY53是该途径的直接底物。此外，OsGSK2还能磷酸OsMAPKK4抑制OsMAPK6 活性，这表明OsGSK2介导的BR信号传导也可能介入了MAPK信号通路。总之，本项目揭示了OsWRKY53整合了BR和MAPK信号，解析了OsWRKY53正向调控水稻株型和粒型的分子机理。