The role of bacterial extracellular RNAs in plant infections with Xylella

病原体的感染成功取决于毒力因子，即所谓的效应子，进入宿主细胞以规避植物免疫。自2013年以来，Xylella fastidiosa（Xf）在欧洲成为一种细菌病原体，与橄榄树，杏仁树和柑橘树的毁灭性流行病有关。由于缺乏III型系统及其分泌的效应物，Xf用于抑制宿主免疫的机制仍然没有答案。细胞外囊泡（extracellular vesicles，EVs）是细菌的重要结构，与Xf的毒力密切相关。该子项目将评估来自Xf的EV在宿主感染中的作用。我们最近在拟南芥中建立了Xf感染，并观察了Xf EV的免疫原性和免疫抑制活性。在EV的RNA结合蛋白和RNA的检测表明，EV可以运输细菌胞外RNA（exRNA）物种。我们的目标是确定与Xf疾病相关的EV RNA库，并解决EV RNA对植物免疫系统的调节。为了解决EV RNA种类和宿主靶标的特征在微生物种类中是否共同，我们将在RU 5116中进行比较研究。利用RU5116的研究成果，我们将探索针对Xf的RNA介导的沉默。总之，该子项目将对病原体毒力（特别是Xf）的机制产生新的见解，并最终旨在确定新型病原体效应物和宿主靶点，当靶向这些靶点时，将导致病原体无毒力和植物抗性。

The infection success of pathogens depends on the delivery of virulence factors, so-called effectors, into host cells to circumvent plant immunity. Since 2013, Xylella fastidiosa (Xf) emerged as a bacterial pathogen in Europe associated with devastating epidemics in olive, almond and citrus trees. Lacking a Type III system and its secreted effectors, the mechanism used by Xf to suppress host immunity remain unanswered. Extracellular vesicles (EVs) are important bacterial structures, which have been associated with Xf virulence. This subproject will evaluate the role of EVs from Xf in host infection. We recently established Xf infection in Arabidopsis and observed both immunogenic and immune-suppressive activities of Xf EVs. Detection of RNA-binding proteins and RNAs at EVs suggests that EVs could transport bacterial extracellular RNA (exRNA) species. Our goal is to identify the EV RNA repertoire associated with Xf disease and to address the modulation of the plant’s immune system by EV RNAs. To address whether signatures of EV RNA species and host targets are common across microbial species, we will contribute to comparative studies within the RU5116. Benefitting from RU5116 research, we will explore RNA-mediated silencing against Xf. Together, this subproject will lead to new insights into the mechanisms contributing to pathogen virulence, in particular for Xf, and ultimately aims to identify novel pathogen effectors and host targets that, when targeted, will result in pathogen non-virulence and plant resistance.