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科学家揭示水稻抗病防卫机制
发表日期: 2015-03-30 作者: 王国梁等 文章来源:《PLoS病原体》
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记者近日从中国农科院植物保护研究所了解到,王国梁研究团队对泛素连接酶SPL11底物SPIN6蛋白在水稻抗病调控途径中的作用机理研究取得新进展,并基于研究结果提出调控水稻抗病防卫反应的工作模型。相关研究结果日前在线发表于美国《科学公共图书馆—病原体》上。

泛素蛋白酶体途径是真核生物体内蛋白质翻译后修饰最重要的调控机制之一。泛素连接酶E3在泛素调解的蛋白质降解过程中负责识别特异性的底物蛋白,发挥着重要作用。

水稻稻瘟病和白叶枯病是水稻生产过程中最严重的真菌性和细菌性病害,严重影响着我国的粮食安全生产。前期研究中,王国梁团队发现假病斑突变体SPL11显著增强了对水稻稻瘟病和白叶枯病的抗耐性,SPL11在水稻中与一个RhoGAP蛋白SPIN6相互识别,在SPL11蛋白存在情况下,SPIN6蛋白的积累明显被抑制,说明SPL11可以促进SPIN6的泛素化降解,SPIN6SPL11泛素化的底物蛋白。另一方面,SPIN6蛋白具有RhoGAP活性,并可将活性状态的OsRac1蛋白失活,催化OsRac1蛋白的水解,从而抑制OsRac1介导的水稻抗病防卫反应。该成果对提出新的水稻病害防控策略具有重要意义。(来源:中国科学报 李晨)

 

The RhoGAP SPIN6 Associates with SPL11 and OsRac1 and Negatively Regulates Programmed Cell Death and Innate Immunity in Rice

 

Abstract  The ubiquitin proteasome system in plants plays important roles in plant-microbe interactions and in immune responses to pathogens. We previously demonstrated that the rice U-box E3 ligase SPL11 and its Arabidopsis ortholog PUB13 negatively regulate programmed cell death (PCD) and defense response. However, the components involved in the SPL11/PUB13-mediated PCD and immune signaling pathway remain unknown. In this study, we report that SPL11-interacting Protein 6 (SPIN6) is a Rho GTPase-activating protein (RhoGAP) that interacts with SPL11 in vitro and in vivo. SPL11 ubiquitinates SPIN6 in vitro and degrades SPIN6 in vivo via the 26S proteasome-dependent pathway. Both RNAi silencing in transgenic rice and knockout of Spin6 in a T-DNA insertion mutant lead to PCD and increased resistance to the rice blast pathogen Magnaporthe oryzae and the bacterial blight pathogen Xanthomonas oryzae pv. oryzae. The levels of reactive oxygen species and defense-related gene expression are significantly elevated in both the Spin6 RNAi and mutant plants. Strikingly, SPIN6 interacts with the small GTPase OsRac1, catalyze the GTP-bound OsRac1 into the GDP-bound state in vitro and has GAP activity towards OsRac1 in rice cells. Together, our results demonstrate that the RhoGAP SPIN6 acts as a linkage between a U-box E3 ligase-mediated ubiquitination pathway and a small GTPase-associated defensome system for plant immunity.

 

原文链接:http://www.plospathogens.org/article/fetchObject.action?uri=info:doi/10.1371/journal.ppat.1004629&representation=PDF

 


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