胁迫相关蛋白激酶OsSAPK9调控水稻白叶枯病抗性反应的分子机理

Revealing the pathogenic mechanism of bacteria blight is essential to improvement of resistant varieties, which ensures the food security in China. The sucrose non-fermenting1-related protein kinase 2 (SnRK2s) gene family members are involved in the regulation of abscisic acid (ABA) and response to both biotic and abiotic stresses in plant. However, in rice, the molecular mechanisms are still not clear. In our previous study, we found that OsSAPK9, a SnRK2 member, played a positive role in improving race-specific resistance for bacterial blight in rice. Moreover, OsSAPK9 could interact with OsSGT1 (Suppressor of G2 allele of skp1) both in vivo and in vitro, suggesting that OsSAPK9 and OsSGT1 might form a protein complex to regulate the defense response. In this study, we aim to ascertain whether ABA contributes to the OsSAPK9-mediated defense response, understand the possible molecular mechanisms of bacteria blight resistance mediated by the protein complex of OsSAPK9 and OsSGT1, uncover the putative gene regulatory networks underlying OsSAPK9-mediated defense response, present the crystal structure of the OsSAPK9-OsSGT1 protein complex by LC-MS/MS, transcriptomics, and X-ray diffraction method, etc. Our study will enrich the gene resources of disease-resistance, and provide new information and strategy for improvement of disease resistance in rice.

揭示水稻抗白叶枯病的分子机理，培育抗性水稻品种，有利于保障我国粮食安全。研究表明植物SnRK2基因家族参与ABA信号调控并响应生物胁迫与非生物胁迫，但是水稻中SnRK2家族成员OsSAPK的抗病分子机理尚不明确。前期研究中，申请人通过对RNAi和过表达植株的表型鉴定发现OsSAPK9正向调控水稻对白叶枯病的小种专化抗性，利用酵母双杂交文库筛选获得抗病相关蛋白OsSGT1，并通过蛋白质互作验证及表达分析初步证明OsSAPK9与OsSGT1互作调控水稻白叶枯病抗性反应。本研究拟运用LC-MS/MS、转录组测序、X-射线衍射等技术探明OsSAPK9介导的水稻抗病反应是否依赖于ABA，明确OsSAPK9与OsSGT1互作的分子机制并解析二者蛋白复合体的晶体结构，揭示OsSAPK9调控水稻抗病性的分子调控网络。本研究的实施有助于揭示水稻抗病性的分子机理，为培育抗病水稻品种提供新的基因资源和理论依据。

白叶枯病和盐胁迫是水稻生产的主要限制因素。蔗糖非酵解型蛋白激酶2（SnRK2）是植物特异性丝氨酸/苏氨酸激酶家族的成员，是参与植物发育过程和胁迫反应信号通路的重要组成部分。水稻中有10个SnRK2家族成员，然而它们的功能和分子机制尚不十分清楚。本研究明确了SnRK2家族的OsSAPK9对水稻白叶枯病菌株特异性抗性和耐盐性都具有正调控作用。通过转录组测序发现在盐胁迫和接种白叶枯病菌后，OsSAPK9-RNAi转基因植株与野生型相比分别有404和1324个基因差异表达，这些基因主要涉及植物的基础代谢过程。在盐胁迫和接种白叶枯病菌后，共同检测到65个参与防御反应的差异表达基因。此外，我们通过体内和体外实验进一步证明了OsSAPK9与分子伴侣OsSGT1、OsHsp90可以形成蛋白复合物。过表达OsSGT1会导致水稻耐盐性降低和对白叶枯病的抗性水平提高。因此，OsSAPK9可能是通过与OsSGT1相互作用共同调控水稻抗病和盐胁迫响应的途径，是水稻响应生物与非生物胁迫信号途径的重要节点。我们基于水稻重测序种质资源分析了OsSAPK9的遗传多样性，发掘出OsSAPK9抗病和耐盐的优异单倍型OsSAPK9-Hap2。该研究揭示了OsSAPK9介导的水稻响应生物胁迫和非生物胁迫的分子机理，为培育抗逆水稻品种提供了新的基因资源和理论依据。

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