感病因子RTP1调控植物抗寄生疫霉菌的机理研究

Oomycetes, particularly Phytophthora species, cause serious crop diseases, such as potato late blight, and threaten the sustainable crop production worldwide. Due to the prominent problem of virulence variation and loss of genotype-specific resistance, understanding and utilization of novel factors that confer broad-spectrum and durable resistance have been a central focus in the field of plant-oomycete interaction. Based on the compatible interaction between Phytophthora parasitica, a model oomycete pathogen, and the reference plant Arabidopsis thaliana, we have previously identified a novel susceptibility factor, namely RTP1 (Resistance to P. parasitica 1), which encodes an Endoplasmic Reticulum (ER) localized protein. The loss-of-function rtp1 mutant showed resistance against P. parasitica and several other biotrophic pathogens. Additionally, our preliminary data indicated that RTP1 might play an important role in sensing ER stress and regulating ER stress response (UPR). In this study, we aim at i) further characterization of the ER stress in A. thaliana WT Col-0 and rtp1 mutant upon infection by P. parasitica; ii) confirmation of the function of RTP1 in ER stress sensing during plant- P. parasitica interaction; iii) dissection of how RTP1 orchestrates key factors of UPR pathways and coordinately regulates plant immunity. The mechanistic studies will facilitate understanding of how RTP1 negatively regulates plant immunity to P. parasitica. The proposed research is expected to facilitate development of novel strategies for the utilization and molecular design of genetic resources required for crop disease resistance breeding.

疫霉属（Phytophthora）卵菌引致马铃薯晚疫病等作物灾难性病害，严重威胁作物的可持续生产。由于病菌毒性变异和品种抗病性丧失问题突出，因此，鉴定和利用植物广谱和持久抗性的关键因子一直是作物-病原卵菌互作研究的热点及难点问题。本项目拟以前期研究中鉴定到的一个拟南芥中编码内质网膜蛋白的新型感病因子RTP1为研究对象，从rtp1突变体对内质网应激呈现的一系列变化特征为入手点，对比分析拟南芥野生型Col-0与rtp1突变体在接种疫霉菌后内质网应激的发生特征，明确RTP1在植物与疫霉菌互作中感应内质网应激的功能，并进一步解析RTP1与内质网应激效应UPR信号的关键因子如何协同调控植物对疫霉菌的免疫应答，从而深入揭示感病因子RTP1负调控植物抗寄生疫霉菌的机理。本项目的研究为作物抗病资源的挖掘与利用以及作物抗病分子设计提供理论依据和新策略。

疫霉属卵菌引致马铃薯晚疫病等作物灾难性病害，严重威胁作物可持续生产。针对病菌毒性变异导致的品种抗病性丧失问题，通过修饰寄主感病因子或免疫负调控因子赋予植物广谱持久抗性，是作物抗病性改良的重要途径。本项目聚焦定位于内质网膜的感病因子RTP1，围绕其如何参与负调控植物抗疫霉菌的作用机理开展研究，取得了以下重要进展：①在细胞水平和分子水平上证明了疫霉菌侵染可诱发植物细胞的内质网应激，RTP1响应内质网应激而发生亚细胞定位改变，并且RTP1参与负调控UPR相关基因的诱导表达。②阐明RTP1通过削弱IRE1激酶自我磷酸化水平及其介导的bZIP60mRNA剪切，进而增强UPR关键感应因子bZIP60的稳定性；同时，RTP1能够与UPR关键感应因子bZIP28特异性互作，并增强其蛋白稳定性；从而明确了RTP1参与调控IRE1-bZIP60和bZIP28介导的植物内质网应激信号通路。③证实了RTP1缺失突变体响应寄生疫霉侵染所呈现的抗病性、内质网应激相关免疫基因的诱导表达以及活性氧迸发等免疫反应在rtp1bzip60和rtp1bzip28双突变体中均有明显削弱。揭示了bZIP60和bZIP28为RTP1介导的植物免疫功能所必需。④基于转录组分析，鉴定到RTP1显著调控的内质网应激相关免疫基因WRKY33等；通过分析启动子区控制元件及双荧光素酶报告系统，揭示了bZIP28转录因子与WRKY33启动子区存在结合，而RTP1能够影响其结合。⑤拓展分析鉴定到一个CYP450新基因为作用于RTP1下游的免疫正调控因子，细胞死亡相关因子VPE和BI-1在rtp1抗病性和细胞死亡中具有重要作用。综上，本研究阐明了感病因子RTP1与内质网应激信号协同调控植物免疫的作用模式，为RTP1负调控植物免疫的作用机制提供了新见解；也为作物抗疫病的遗传改良提供了有价值的基因资源与新途径。