How do plant resistance proteins activate defence gene expression upon effector perception?

植物抗病(R)蛋白使植物能够检测特定的病原菌效应分子，然后激活防御，但防御激活对R蛋白激活的机制(效应器触发免疫，简称ETI)知之甚少。拟南芥RPS4和RRS1抗性基因共同作用检测到两种不同的细菌效应蛋白：来自假单胞菌的AvrRps4和来自Ralstonia sp.的乙酰基转移酶PopP2。RPS4是一种典型的TIR-NB-LRR R蛋白，但RRS1TIR-NB-LRR R蛋白也携带一个WRKY DNA结合域，作为检测AvrRps4和PopP2存在和/或活性的“诱饵”(Williams等人2014年；10.1126/Science.1247357Sarris等人2015年；10.1016/j.cell.2015.04.024)。RPS4/RRS1激活防御导致快速诱导约40个ETI基因，包括水杨酸生物合成基因、其他防御酶和转录调节基因(Sohn等，2014年/Journal al.pgen.1004655)。这项研究的目的是了解RPS4/RRS1如何在感受效应时激活拟南芥中这40个共同调节的ETI基因。学生将测试在激活后，RPS4/RRS1是否与ETI防御过程中诱导的基因的染色质状态相关联并改变。该项目将定义ETI诱导基因激活时染色质的变化，并分析与防御基因启动子相关的转录因子。

Plant disease resistance (R) proteins enable plants to detect specific pathogen effector molecules, and then activate defence, yet mechanisms of defence activation upon R protein activation (Effector-Triggered Immunity, or ETI) are poorly understood. Arabidopsis RPS4 and RRS1 resistance genes act together to detect two different bacterial effector proteins, AvrRps4 from Pseudomonas sp., and PopP2, an acetyltransferase, from Ralstonia sp.. RPS4 is a typical TIR-NB-LRR R protein, but the RRS1 TIR-NB-LRR R protein also carries a WRKY DNA binding domain, that acts as a "bait" that detects the presence and/or activity of AvrRps4 and PopP2 (Williams et al 2014; 10.1126/science.1247357 Sarris et al 2015; 10.1016/j.cell.2015.04.024).Activation of defence by RPS4/RRS1 results in rapid induction of ~40 ETI genes, including genes for salicylic acid biosynthesis, other defence enzymes and transcription regulators (Sohn et al, 2014 10.1371/journal.pgen.1004655). The goal of the studentship is to understand how RPS4/RRS1 activates these ~40 coregulated ETI genes in Arabidopsis upon effector perception. The student will test if upon activation, RPS4/RRS1 associates with and changes the chromatin state of genes that are induced during ETI defence. The project will define changes in chromatin at ETI-induced genes upon activation, and analyse transcription factors that associate with defence gene promoters.