丝裂原活化蛋白激酶级联调控水稻-病原互作机理研究

Mitogen-activated protein kinase (MAPK) cascades are evolutionarily conserved in eukaryotes and play important roles in different biological processes. Rice genome has 74 MAPK kinase kinase (MAPKKK) genes, 8 MAPK kinase (MAPKK) genes, and 17 MAPK genes, suggesting that the encoding products of these genes may consist of a large number of MAPK cascades, However, the knowledge of rice MAPK cascades is large unknown and no single MAPK cascade has been revealed in rice-pathogen interactions. In this project, we will use two our previous reported MAPK cascades kinases and two preliminary studied MAPK kinases as the starting point to identify new MAPK cascades kinases, which physically interact and have phosphorylation relationship with at least one of the four starting kinases. We, then, will study the roles of these candidate kinases in rice response to bacterial blight, bacterial streak, blast, and false smut diseases, and identify the MAPK cascades involved in rice-pathogen interactions. This project will facilitate the elucidation of the molecular mechanisms of rice resistance to diseases. It may also help to formulate a MAPK cascade based strategy for rice improvement.

丝裂原活化蛋白激酶（MAPK）级联是真核生物中保守的信号传递通路，参与调控各种各样的生理活动。水稻基因组中共计有99个不同类型的MAPK级联基因，推测它们可以组成大量MAPK级联通路。但是，人们对水稻MAPK级联了解甚少，在水稻--病原互作中还没有报道一条完整的MAPK级联通路。本项目拟以我们已经报道的两个MAPK级联激酶和两个初步鉴定功能的MAPK级联激酶为出发点，鉴定与它们物理互作和有磷酸化关系的新的MAPK级联激酶；确定它们在水稻抵抗白叶枯病、细菌性条斑病、稻瘟病和稻曲病中的作用；分析这些候选MAPK级联激酶在调控抗病反应中的上下游关系，确定调控抗病反应的完整MAPK级联通路。本研究结果不仅将有助于揭示MAPK级联在不同水稻--病原互作系统中的作用，使人们深入了解水稻抗病的分子机理，具有重要科学意义；也将有助于育种工作者依据不同抗病机理特点，选择性地对水稻的抗性进行精准改良。

植物丝裂原活化蛋白激酶MAPK在抗病中发挥重要作用，但是水稻MAPK成员众多，是否有成员以及如何参与水稻对不同病原菌抗病过程，目前知之甚少。我们研究重要结果包括：1）解析了水稻MPKK10.2-MPK6/MPK3信号级联正向调控水稻抗细菌性条斑病的分子机理。我们发现MPKK10.2正向调控水稻对细菌性条斑病的侵染，通过激酶活性实验结合遗传学手段，进一步发现MPKK10.2通过分别激活MPK6和MPK3来分别调控水杨酸和脱落酸信号路径，进而调控水稻对细菌性条斑病的侵染过程；2）发现水稻OsMAPKKK43基因负调控对白叶枯病的抗性，进一步发现OsMAPKKK43-OsMAPKK4-OsMAPK6信号级联反应在水稻抗白叶枯病信号传递和启动基础免疫反应中的重要作用；3）解析了MPKK5-MPK6促进水稻抗白叶枯病的分子机理。本项目发现，MPKK5正向调控水稻对白叶枯病的抗性，遗传学和生化实验发现，MPKK5作用于MPK6的上游且激活MPK6的激酶活性。进一步的结果显示，MPKK5-MPK6信号级联通过促进ROS的产生增强水稻对白叶枯病的抗性。目前正在深入发掘MPKK5-MPK6促进ROS产生的机制，以进一步解释其参与调节水稻抗病的分子机制；4）解析了MPKK1/MPKK6-MPK4信号级联正向调控水稻对白叶枯病抗性的机理。已发表的结果显示MPK4能够促进水稻对白叶枯病的抗性，本项目在此基础上，通过激酶活性实验以及遗传学手段发现MPKK1/MPKK6共同作用于MPK4的上游且促进水稻对白叶枯病的抗性。进一步通过酵母筛库得到了MPK4的两个底物VQ14/VQ32，发现这两个基因正向调控水稻对白叶枯病的抗性，而且MPKK1/MPKK6-MPK4对这两个底物的磷酸化是其发挥抗病功能所必需的。