BR信号通过转录因子GLK1调控叶绿体发育的研究

Plant steroid hormones, brassinosteroids (BRs), play essential roles in modulating numerous developmental processes, including photomorphogenesis. But the molecular mechanism how BRs regulates photosynthesis is not known. Compared with wild type, BR signal pathway mutants bri1-5 and bes1-D displayed changed chlorophyll content. Arabodopsis thaliana GOLDEN2-LIKE 1(GLK1) transcription factor，which is required for chloroplast development, was identified through chromatin immunoprecipitation (ChIP) experiments as a direct target gene of BES1. Expression of GLK1 is repressed by BRs or BES1. Many Light Harvesting and Chlorophyll Biosynthesis Genes regulated by GLK1 also are BR response genes. We will test whether GLK1 functions to regulate the expression of a subset of BR target genes which are essential for chloroplast development. And we will use GLK1 overexpression transgenic plants and glk1glk2 double mutant to confirm effects of GLK1 in BR pathway. We also will perform protein interaction experiments to determine if GLK1 can interact with BES1 and the interaction functions in GLK1 binding ability. Next we will perform electrophoretic mobility shift assays to test whether BES1 and GLK1 can bind the photosynthesis related genes promoters to regulate their expression together and/or separately. Our results therefore will establish a new mechanism by which GLK1, a direct target of BES1, functions to amplify BR signaling in regulating chloroplast development.

植物激素油菜素内酯（BRs）可以调控植物的许多生长发育过程，其中就包括光合作用。但是BR信号调控光合作用的分子机理还不是很清楚。拟南芥中，与野生型相比，BR信号突变体bri1-5和bes1-D中的叶绿素含量都发生了变化。我们研究发现GLK1是BES1的目标基因，GLK1所调控的光合基因的表达受到BR信号的影响，因此推测BR信号可能通过调控GLK1来影响叶绿体发育。我们将通过构建GLK1过表达（GLK1OX）和缺陷（glk1glk2）植物来探究GLK1在BR调控叶绿体发育过程中的作用。我们拟研究GLK1是否与BES1可以一起绑定在叶绿体发育相关基因的启动子上共同调控目标基因的表达。验证GLK1与BES1的相互作用，BES1是否可以通过结合GLK1来降低其转录活性，从而抑制叶绿体发育相关基因的表达。这些研究对于丰富和完善BR信号调控叶绿体发育的分子机制，更好了解BRs的生物学效应具有指导意义。

植物激素油菜素内酯（BRs）可以调控植物的许多生长发育过程，其中就包括光合作用。但是BR信号调控光合作用的分子机理还不是很清楚。拟南芥中，与野生型相比，BR信号突变体bri1-5和bes1-D中的叶绿素含量都发生了变化。我们研究发现GLK1是BES1的目标基因，GLK1所调控的光合基因的表达受到BR信号的影响，因此推测BR信号可能通过调控GLK1来影响叶绿体发育。我们通过构建GLK1过表达（GLK1OX）和缺陷（glk1glk2）植物来探究GLK1在BR调控叶绿体发育过程中的作用。我们的研究结果发现BR可以抑制叶绿体发育以及叶绿素的积累，而在BR信号缺陷突变体bri1-5中，叶绿体发育对BR不敏感。这些结果都说明BR或者BR信号调控叶绿体发育过程。染色质免疫共沉淀结果表明GLK与BES1可以一起绑定在叶绿体发育相关基因的启动子上共同调控目标基因的表达。GLK1是BES1的直接靶标基因，BES1可以通过抑制GLK1来降低其转录水平，从而抑制叶绿体发育相关基因的表达。这些研究对于丰富和完善BR信号调控叶绿体发育的分子机制，更好了解BRs的生物学效应具有指导意义。