水稻腺苷酸环化酶结合蛋白调控微丝动态的分子机制研究

Various actin binding proteins (ABPs) act coordinately to regulate actin dynamics to perform numerous actin-based functions. It remains to be a major research topic regarding the dissection of the functions and mechanisms of action of these ABPs as well as their coordination in cell biology. Cyclase-associated protein (CAP) is an important ABP that binds to actin monomers and regulates nucleotide exchange on actin as well as promotes actin assembly and disassembly. To date, the physiological functions and mechanisms of action of CAP remain poorly characterized in plants. Loss of CAP in Arabidopsis caused very severe growth and developmental phenotype that prevents further dissection of its action mechanism. By comparison, the rice genome encodes two CAP genes, OsCAP1 and OsCAP2, and the preliminary study showed that loss of each rice CAP gene only caused mild growth and developmental phenotype, which provides the possibility of dissecting the underlying precise mechanisms of action of plant CAP. This project aims to dissect the functions and mechanisms of action of rice CAP in combination of various experimental approaches, the related study will enrich our knowledge regarding the mechanisms of action and functional evolution of CAP in general. Meanwhile, it will enhance our understanding regarding the similarities and differences of the regulation mechanisms of actin dynamics between dicots and monocots.

各种微丝结合蛋白协作调控微丝动态组装以完成各种微丝介导的生理功能，研究它们的功能和作用机制以及相互之间的协作机制是细胞生物学领域的重要研究内容。其中腺苷酸环化酶结合蛋白（cyclase-associated protein; CAP）和肌动蛋白单体结合，促进肌动蛋白核苷酸交换，进而调控微丝的聚合与解聚。植物CAP的生理功能和作用机制相对不清楚，期待深入研究。拟南芥CAP功能缺失表型严重，对深入阐明其作用机制造成了一定的障碍。而水稻基因组则编码两个CAP基因，我们初步的研究发现降低它们的表达分别引起了一定程度的发育缺陷，为深入解析植物CAP的作用机制提供了条件。本项目拟以水稻为材料，综合多种研究方法对CAP的功能和作用机制进行深入研究，相关研究对于理解CAP的普遍作用机制和功能进化具有重要的科学理论意义，同时也将增进人们对单子叶和双子叶植物微丝骨架动态组装调控机制的异性和共性的认识。

微丝细胞骨架参与调控植物生长发育的许多重要的生理过程。微丝动态特性的调控是通过与各种肌动蛋白结合蛋白的相互作用来实现的。其中腺苷酸环化酶结合蛋白（cyclase-associated protein; CAP）和肌动蛋白单体结合，促进肌动蛋白核苷酸交换。但有关水稻CAP的生化性质和生理功能还不清楚。对OsCAPs蛋白体外生化分析表明，OsCAP1和OsCAP2都能够结合肌动蛋白单体，抑制微丝的成核及聚合过程，促进G-actin的核苷酸交换。OsCAP2的活性高于OsCAP1。另一方面，我们对OsCAP1在植物体内的功能进行了研究。OsCAP1表达水平的降低影响了水稻花粉微丝骨架的含量和排布，导致花粉的活性及萌发率降低、结实率下降、穗长变短。而泛素启动子驱动的OsCAP1过表达不仅影响了花粉活性、萌发率，且影响了水稻的生长发育过程。综上所述，本项目的研究有助于我们理解微丝动态调控的机制，同时也丰富了我们对CAP蛋白家族的功能及作用机制的理解。