影响生长素运输的新受体激酶调控大豆避荫反应的分子机理研究

Shade stress is the main environmental limiting factor for improvement of soybean yield in soybean intercropping system. It was demonstrated that normal auxin polar transport is indispensible for shade avoidance, and phosphorylation is critical for activation of auxin transporters, in which receptor kinase plays one of the most important roles. However, which receptor kinases specifically regulate auxin transporters upstream in shade avoidance signaling pathways is still unknown. We have discovered a new soybean receptor kinase and eight auxin transporters. we found that auxin polar transport is controlled by this new receptor kinase. In this proposal, we will screen and verify the new members of the receptor kinase complex and their target auxin transporters via yeast-two hybrid and co-immunoprecipitation based on our previous studies. we will also make attempt to explore the molecular mechanisms underlying the new receptor kinase and auxin transporters together in regulating shade avoidance with approaches of genetics including gene overexpression and silence, plant physiology, and verify the phenotypes of the mutants of this receptor kinase by shading in intercropping system. In addition, our proposal is also aimed to elucidate the mechanisms of phosphorylation of auxin transporters triggered by receptor kinase with methods of biochemistry. These studies would give us new insight into functions of soybean receptor kinase in regulating shade avoidance and make a foundation for further analyzing the molecular network of shade avoidance in soybean. Moreover, it would provide more theoretical proofs for new shade-tolerant soybean cultivars improvement and breeding via biotechnologies.

荫蔽胁迫是套作大豆产量提升的主要环境限制因子。研究表明，正常的生长素极性运输在植物避荫反应中不可或缺，磷酸化是生长素运输蛋白极为重要的活化方式，受体激酶在该磷酸化过程中甚为重要，然而避荫反应信号通路中生长素运输蛋白与受体激酶的特异关系还不清楚。我们前期从荫蔽诱导的大豆磷酸化组中找到了一个新的受体激酶和8个生长素运输蛋白，发现生长素极性运输受到该受体激酶调控。本项目将在此基础上用免疫共沉淀和酵母双杂交方法验证该受体激酶与其靶标生长素运输蛋白的互作关系，并进一步筛选该受体激酶复合物新成员；综合运用分子遗传学、生理学与细胞生物学等手段研究该受体激酶与生长素运输蛋白共同调控大豆避荫反应的分子生理机制，并在大田套作条件下验证该受体激酶突变体表型；用生化手段揭示受体激酶特异激活生长素运输蛋白的磷酸化机制，为进一步解析大豆避荫反应的分子调控网络奠定基础，也为耐荫大豆新品种培育和生物技术改良提供理论依据。

荫蔽胁迫是套作大豆产量提升的主要环境限制因子。避荫反应的发生依赖各组织细胞间的相互合作和信号交流，而信号的交流很大程度上依赖植物类受体激酶的参与，但是很少有报道证明类受体激酶参与植物避荫反应。申请人在研究中发现类受体激酶ER和SHIRK1参与避荫反应，并且发现生长素和赤霉素对ER调控避荫反应的过程具有显著影响，随后通过遗传实验发现ER参与的避荫反应部分依赖光敏色素PHYB，而生长素转运对SHIRK1调控的避荫反应具有显著影响。并且通过GUS报告基因发现大豆ER和SHIRK1基因响应荫蔽信号，同时在蛋白磷酸化组学中也筛选到新的参与大豆避荫反应的类受体激酶。而本研究在前期已有的基础上进一步丰富了类受体激酶ER参与植物避荫反应的信号调控网络，发现了其上游的一个分泌多肽也一起参与该过程，此外，还发现光敏色素因子PHYB与ER存在相互作用，并首次发现类受体激酶ER能在细胞核定位。此外，在实验过程中意外发现SHIRK1参与渗透胁迫下的种子萌发过程，并通过生理及生化实验首次证明SHIRK1与CAM7互作并调控种子萌发。