独脚金内酯（strigolactones, SLs）是近年来发现的植物激素，它主要抑制分枝和下胚轴生长、促进束间形成层的发育和种子萌发等。SL结合到受体AtD14，促进MAX2对底物的降解，从而调控下游组分。最近申请人发现油菜素甾醇（Brassinosteroids, BRs） 信号转导途径的转录因子BES1与MAX2互作，并作为MAX2的底物抑制分枝，但是MAX2和BES1参与SL和BR信号通路并调控植物生长发育的机制未知。我们和他人的前期研究发现，BES1和MAX2可能也参与最新发现的另一种激素Karrikin的信号转导。本项目将以拟南芥为材料，采用遗传学、细胞生物学、生物化学、发育生物学和生物信息学等方法，阐明SL、BR和Karrikin 信号转导途径中BES1和MAX2与AtD14和SMXLs的遗传和生化关系，建立它们的信号转导网络，并揭示其调控植物分枝和次生生长的细胞和分子机制。

Strigolactones (SL) are a class of the most recently identified phytohormones, which play essential roles in plant development, such as inhibiting shoot branching and hypocotyl elongation, and promoting interfascicular cambium development and seed germination. SL binding to AtD14 promotes the degradation of F-box protein MAX2’s substrates to regulate SL-regulated gene expression. Recently, we found that BES1, a major transcriptional factor of brassinosteroid (BR) signaling pathway, interacts with MAX2 and acts as its substrate to regulate SL-responsive gene expression. But the underlying mechanisms of how SL and BR signaling pathways interact and control specific developmental processes is poorly understood. Based on our unpublished data and other known evidence, BES1 and MAX2 may be signaling components of karrikin, another newly identified phytohormone discovered in smoke to promote seed germination. In this proposed study, by using the approaches of genetics, cell biology, biochemistry, developmental biology and bioinformatics, we propose to investigate the genetic and biochemical relationship among BES1, AtD14 and SMXLs to establish the signaling network of SLs, BRs, and karrikin, and uncover the cellular and molecular mechanisms of their regulation on shoot branching and secondary growth.