植物发育可塑性的根本在于植物能随时根据周围环境和发育信号来调控自身分生组织的起始与重建，进而决定其器官发生、成熟和衰老等进程。叶腋分生组织是位于叶腋处的细胞被特异激活分裂形成的干细胞组织，是植物分枝形成的根源，对作物的产量有重要的调控作用。油菜素内酯是一种重要的植物激素，调控着众多的植物学发育过程。申请人前期的研究工作显示油菜素内酯对植物叶腋分生组织的起始和分化有明显的调控作用。为解析油菜素内酯对叶腋分生组织活性的调控机理，在本项目中申请人利用核糖体亲和层析技术分析了油菜素内酯在叶腋分生组织中特异表达调控的基因，并对其中的一些关键基因进行了深入研究，以期阐明油菜素内酯在叶腋分生组织起始和分化过程中调控的分子机制，为我们下一步利用油菜素内酯来改良和设计合理的作物株型提供理论基础和技术保障。

Plant shoot branching pattern affects plant architecture and is pivotal for developmental plasticity and crop yield. Shoot branches develop from axillary meristems (AMs) that initiated in the boundary zone between leaf primordia and the shoot apex, which is regulated by multiple endogenous phytohormonal signals and different environmental cues. Our previous study indicated that brassinosteroid, a key phytohormone for plant growth and development, play an important role for the initiation and differentiation of AM. Here in this proposal, we will take advantage of the genetic and genomic tools to gain a deep insight into the mechanism of brassinosteroid regulation of AM initiation. The specific aims in this proposal are to (1) elucidate the molecular network for BR regulation of AM activity using genetic analysis of interactions between BR-related mutants and known AM mutants, (2) genomic analysis of AM cell-specific transcription network controlled by BZR1 and BAEs, and (3) elucidate the functions of BZR1-targetd transcription factors in AM initiation. Our long-time goal is to define the molecular mechanisms by which BR regulates AM initiation and differentiation, and provides some new tools for breeding high-yield crops.