The contribution of SERK family receptors to immunity against Xylella fastidiosa

植物病害是对全球粮食安全的重大威胁。欧洲“优先害虫名单”上的病原体之一是苛养木杆菌。这种由昆虫传播的细菌是橄榄快速衰退综合征（OQDS）的病因，也是过去8年橄榄快速衰退综合征爆发的重要原因。管理OQDS的可持续策略是在易感宿主中培养抗病能力。然而，目前鉴定出的抗油橄榄品种很少，传统的育种方法将是长期的，很少利用植物免疫机制的分子知识。本项目将评价在易感和抗性橄榄中控制苛养弧菌感染的过程。在遗传模型拟南芥中建立了苛养双歧杆菌感染，我们发现油菜素内酯不敏感的1-相关激酶（BAK1）控制苛养双歧杆菌感染的成功。BAK1属于富含亮氨酸的重复受体样激酶家族，称为体细胞胚胎发生受体激酶（SERK）。BAK1/SERK3与模式识别受体（PRR）如EF-Tu受体（EFR）形成复合物，诱导PRR触发免疫（PTI）。橄榄转录组分析显示，大部分OeSERK3同源物在易感品种“油橄榄”中下调。在耐药的“Leccino”中，更多的OeSERKs在对苛养x虫感染的反应中上调，我们推测其中一些可能与PRRs一起起共受体的作用。我们还建立了抗性和易感橄榄品种的愈伤组织和细胞悬浮培养，我们探索了原型PTI反应的特征以及转基因橄榄的产生，即用EFR转化。我们的目标是回答两个关键问题：OeSERKs如何调节PTI和对苛养x虫感染的反应？分析橄榄的OeSERKs和比较栽培品种将揭示候选基因进行功能分析。OeSERK相互作用蛋白将在两个品种中进行探索。2. 与橄榄免疫和木杆菌感染成功相关的PTI特征是什么？比较抗性和易感橄榄品种的转录组分析，以及评估橄榄家族中对一组免疫触发因素的原型PTI反应，可能会为这个问题提供见解。作为一种多年生木本非模式植物，我们的总体目标是更好地了解橄榄的PTI，并探索PTI的栽培和家族遗传多样性，以分析PTI和鉴定与免疫相关的分子成分。完成后，该项目将为橄榄免疫系统提供新的见解，并确定参与对苛性葡萄球菌反应的OeSERKs和相互作用因子。了解免疫共受体的多样性对于设计易感作物基因型的抗性至关重要。

Plant diseases represent a significant threat to global food security. One of the pathogens ranked in the “list of priority pests” for Europe is Xylella fastidiosa. This insect-transmitted bacterium is the cause of the OLIVE QUICK DECLINE SYNDROME (OQDS) and important for outbreaks over the past eight years. A sustainable strategy to manage OQDS is to breed disease resistance into susceptible hosts. However, only few resistant olive cultivars have been identified and classical breeding approaches will be long-term, taking little advantage of the molecular knowledge on plant immune mechanisms. This project will evaluate the processes that control the infection of X. fastidiosa in susceptible and resistant olive. Having established X. fastidiosa infection in the genetic model A. thaliana, we identified that BRASSINOSTEROID INSENSITIVE 1-ASSOCIATED KINASE (BAK1) controls X. fastidiosa infection success. BAK1 belongs to the family of leucine-rich repeat-receptor-like kinases called SOMATIC EMBRYOGENESIS RECEPTOR KINASEs (SERK). BAK1/SERK3 forms complexes with pattern recognition receptors (PRR) such as the EF-Tu RECEPTOR (EFR) to induce PRR-triggered immunity (PTI). Transcriptome profiling in olive revealed that most OeSERK3 homologues were downregulated in the susceptible “Ogliarola salentina” cultivar. In resistant “Leccino”, more OeSERKs were upregulated in response to X. fastidiosa infection, and we speculate that some could function as co-receptors with PRRs. We also established callus and cell suspension cultures of both resistant and susceptible olive cultivars, which we explore for characterizing prototypic PTI responses as well as the generation of transgenic olives, i.e. transformed with EFR. Our goal is to answer two key questions: 1. How do OeSERKs regulate PTI and the response to X. fastidiosa infection? Profiling OeSERKs from olive and comparing cultivated varieties will reveal candidate genes subjected to functional analysis. OeSERK interacting proteins will be explored across the two cultivars. 2. What are the PTI signatures associated with olive immunity and Xylella’s infection success? Comparative transcriptome profiling of a resistant and susceptible olive cultivar together with assessing prototypic PTI responses to a panel of immune triggers in the olive family are likely to provide insights into this question. Being a woody perennial and non-model plant, our overall aim is to better understand PTI in olive and explore the cultivar and family genetic diversity for PTI profiling and the identification of molecular components associated with immunity. At its completion, this project will lead to new insights into the olive immune system and identify OeSERKs and interactors involved in the response to X. fastidiosa. Understanding immune co-receptor diversity is essential to engineer resistance into susceptible crop genotypes.