水稻SnRK2亚族蛋白MISRK1对Chitin激发免疫反应的分子调控

Chitin-triggerred immunity contributes to the base resistance against rice blast disease caused by Magnaporthe oryzae (M. oryzae). The signal perceived by LysM proteins (LYPs), such as CEBiP, OsLYP4, OsLYP6 and their regulating receptor kinase, LysM-RLK1(CERK1), through recognizing the molecule chitin, was then transduced via a MAPK cascade to actviate downstream immune responses. Recent studies identified the receptor-ike cytoplasmic kinases (RLCKs), OsRLCK185, OsRLCK55 and OsLRCK176, from RLCK VII subfamily, as regulators required for chitin-elicited signaling. Members of the sucrose nonfermenting 1-related protein kinase 2 (SnRK2) were previously identified as key regulators involved in plant response to abiotic stresses and abscisic acid (ABA)-dependent plant develpoment. It is unknown whether they play roles in immunities, such like that elicited by chitin. When analyzing the expression of ten SnRK2 genes in rice, we identified one of them (named MISRK1), of which the transcription level was induced post inoculation with M. oryzae. We then found that the rice plant silenced for MISRK1 exhibited compromised resistance against M. oryzae and chitin-triggerred immunity. Here, we aim to discover the molecular mechanism of MISRK1 in regulation of immunity in rice through revealing its function in chitin-triggerred immunity, identifying its key interacting proteins and phosphorylated proteins, and elucidating the signalings and pathways involved in the immunity regulated by MISRK1. Our study will provide basic knowledges in understanding the chitin-triggerred immunity and potentially offer novel strategies for breeding rice with broad-spectrum resistance against M. oryzae.

几丁质（Chitin）激发的免疫反应对水稻稻瘟病基础抗性起着重要的调控作用。Chitin信号在水稻LysM蛋白如CEBiP识别后，通过MAPK级联放大及激酶OsRLCK185和OsLRCK176等调节以激活下游的防卫反应。植物特有的蔗糖非酵解激酶SnRK2亚族蛋白主要负责调控植物对非生物胁迫和ABA介导的生长发育。尚未报道其对植物免疫反应的调节作用。通过分析水稻中10个SnRK2成员的表达，我们发现其中SnRK2亚族基因MISRK1的转录表达受稻瘟病菌诱导，MISRK1抑制表达能显著降低水稻对稻瘟病的抗性以及Chitin激发的免疫反应。本项目拟证实MISRK1对Chitin激发免疫反应的调控作用，鉴定MISRK1的关键互作蛋白和磷酸化蛋白，揭示MISRK1对免疫反应调控的信号通路和生物进程，从而阐述MISRK1调控免疫反应的分子机制，为水稻稻瘟病广谱抗病理论研究与实际应用奠定基础。

水稻病害是影响水稻产量的致命因素之一，对水稻免疫防御反应机制的研究，对培育高产抗病水稻的培育具有重要意义。磷酸激酶蛋白在植物中大量存在，参与到了植物体生命活动的多个过程。通过本项目的实施，我们对水稻磷酸蛋白激酶MISRK1的生化机制及遗传学功能进行了系统的研究。发现MISRK1是一个胞质定位的磷酸激酶，其激酶活性受到几丁质Chitin的诱导。MISRK1表达量的下调，会削弱水稻对稻瘟病菌的免疫反应。进一步遗传学分析表明，MISRK1是水稻稻瘟病抗性的正调控因子。通过酵母双杂交实验，我们筛选得到了一个与MISRK1存在相互作用的蛋白，将其命名为IM1。IM1可以与MISRK1在体内相互作用，协同调控水稻稻瘟病抗性。综上所述，我们的研究表明MISRK1作为一个磷酸激酶，对水稻稻瘟病抗性具有重要的调控作用。本研究丰富了水稻免疫反应理论，为培育高产高抗水稻提供了重要基础。