新型抗病蛋白WAR1激活拟南芥先天免疫的分子机制

跨膜锚链（ANKR-TM）蛋白在植物中广泛存在，目前尚无ANKR-TM蛋白做为抗病蛋白参与植物先天免疫的报道。课题组发现拟南芥多数生态型含有一个主效抗病位点可特异性限制携带hopW1-1效应子的病原细菌的生长；对该位点进行图位克隆获得了一个编码ANKR-TM蛋白的抗病基因WAR1；经三维结构模型比对发现WAR1与动物瞬时受体电位离子通道蛋白TRPA高度相似。进一步研究显示：WAR1与效应子蛋白 HopW1-1在细胞内直接互作，互作早期即可上调钙离子信号通路并且需要蛋白磷酸酶参与激活先天免疫。以此为基础，本项目拟1）鉴定磷酸化WAR1的蛋白激酶和关键的磷酸化修饰位点；2）通过电生理学研究明确WAR1的钙离子通道活性；3）通过研究HopW1-1对WAR1磷酸化和离子通道活性的影响揭示WAR1介导植物先天免疫的分子机制。本研究将为认识病菌效应子触发的植物免疫机制和挖掘新型抗病基因开辟新途径。

The genes encoding ankyrin-repeat transmembrane proteins (ANKR-TM) broadly exist in monocot and dicot plants and their role as disease resistance gene conditioning innate immunity specific to pathogen effectors is still unknown. We have uncovered a genetic locus, which is widely distributed in most Arabidopsis ecotypes, that restricts the growth of bacterial strains carrying the effector gene hopW1-1. The molecular cloning of the locus identified the disease resistance gene WAR1 (hopW1-1 activated resistance 1) encoding an ANKR-TM protein. The similarity search based on three-dimensional structural models revealed that WAR1 was highly similar to the transient receptor potential A (TRPA) ion channel found in animals. Further investigations showed: WAR1 directly interacted with HopW1-1 in vivo and in vitro; the protein phosphatase 2C family protein WIN2 was required for the activation of immunity by the WAR1/HopW1-1 interaction; the majority of the upregulated defense-related genes were found to be involved in calcium signaling pathways. Based on these observations we propose to identify the protein kinase that phosphorylates WAR1 and the phosphorylated sites that are key to the activation of WAR1-mediated immunity, to explore the cation channel activity of WAR1 by electrophysiological studies, and to reveal the molecular basis of HopW1-1 triggered immunity by studying the impact of the interaction among HopW1-1, WAR1, WIN2, and possibly the protein kinase on the phosphorylation status and channel activity of the WAR1 protein. The proposed studies will provide a novel viewpoint of the mechanisms underlying effector-triggered innate immunity thereby opening a new avenue for engineering disease resistance in crop plants.