蛋白激酶XAK3对水稻XA21抗病反应和生长发育的分子调控

Growing rice varieties with healthy growth and development, and broad-spectrum resistance against pathogens is of most importance for agricultural industry. It is well known that brassinosteroids (BRs) play important roles in plant growth, development and responses to environmental cues, but the molecular regulation mediated by BRs in rice is poorly known. The rice leucine-rich repeat receptor kinase XA21 confers high resistance against diverse isolates of Xanthomonas oryzae pv. oryzae, the causal bacterial pathogen to rice. Interestingly, previous studies have shown that the molecular mechanism of the resistance mediated by XA21 is different from either that mediated by classic NBS-LRR type resistance proteins or that mediated by the Arabidopsis PRRs, FLS2 or EFR. Thus, it is of great interest to elucidate the mechanism of XA21-mediated disease resistance. We previously found that the kinase XAK3 interacts with XA21 and positively regulates XA21-mediated disease resistance. We also found that XAK3 interacts with rice brassinosteroid (BR) receptor kinase BRI1 (OsBRI1) and negatively regulates BR signaling. Here, we intend to explore the molecular mechanism of XAK3-mediated regulation on XA21-mediated disease resistance. We will also discover the molecular mechanism that XAK3 negatively regulates BR signaling and the potential relationship between BR signaling and XA21-mediated immunity in rice. Our study will provide the implicit knowledge for breeding rice with broad-spectrum and high resistance to pathogens, and with high yield and quality as well. Through performing this study, we are aiming to publish 3-5 papers, and to train 2-3 graduates and 2-3 post graduates.

水稻的正常生长发育和对外界病原菌的抗性是水稻高产优质的重要保障。油菜素内酯对水稻的生长发育具有重要的调控作用，但其分子机理并不清楚。水稻受体蛋白激酶XA21具有对白叶枯病原细菌广谱高抗性，其抗病机理既不同于NBS-LRR 蛋白介导的抗病反应，又不同于FLS2、EFR等模式识别受体介导免疫反应，因此十分必要阐明水稻XA21的抗病机理。本研究的前期工作表明蛋白激酶XAK3是一个多功能蛋白：一方面，XAK3通过与XA21结合对XA21介导的抗病反应起正调控作用；另一方面，XAK3通过抑制油菜素内酯信号转导以调节水稻的生长发育过程。本研究将从遗传学、植物病理学、分子生物化学等方面揭示XAK3调控水稻受体蛋白激酶XA21介导的抗病反应和调控水稻的生长发育的分子机制，以期指导水稻广谱高抗高产育种。通过该项目的实施，将在国内和国际权威杂志上发表论文3-5篇，培养博士生2-3名，硕士生2-3名。

高产抗病水稻的培育是水稻现代化产业发展的重要环节，胞质类受体蛋白激酶在植物中大量存在，但其功能的报道较少。通过本项目的实施，我们对来源于家族VII的胞质类受体蛋白XAK3 (OsRLCK57) 及其三个同源蛋白OsRLCK107、OsRLCK118和OsRLCK176进行分析和鉴定。发现编码这些蛋白的基因分别抑制表达后都能使水稻表现出对油菜素内酯超敏的表型如叶夹角增大等，表明这些基因通过负调控油菜素内酯介导的信号途径实现对水稻的生长发育的调节，并且这些基因对水稻农艺性状和产量性状具有不同的调控作用，如OsRLCK57主要调控分蘖和穗子的二级支梗，而OsRLCK107和OsRLCK118则主要调控结实率。另外，这些基因的表达受白叶枯病原菌诱导增强，而且对受体蛋白XA21介导的抗病性起着正调控作用。这些基因还参与鞭毛蛋白和几丁质激发的免疫反应。综上所述，我们的研究表明该四个胞质类受体蛋白激酶参与水稻的生长发育和抗病性的调控作用，且油菜素内酯的信号与水稻的免疫反应相互关联。我们的研究为今后培育高产高抗水稻奠定了重要理论基础。