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。在欧洲的“优先有害生物名单”中列出的病原体之一是顶端木霉。这种昆虫传播的细菌是橄榄快速衰退综合症(OQDS)的原因，对过去八年的疫情非常重要。管理OQDS的一个可持续战略是将抗病能力培育成易感宿主。然而，目前已鉴定的抗性橄榄品种很少，经典的育种方法将是长期的，几乎没有利用植物免疫机制的分子知识。本项目将评估控制感病和抗病橄榄中天青霉感染的方法。在建立了甜菜夜蛾的遗传模型后，我们发现油菜素类固醇不敏感的1-相关蛋白激酶(BAK1)控制着甜菜夜蛾的感染成功。BAK1属于富含亮氨酸的重复受体样蛋白家族，称为体细胞胚胎发生受体蛋白(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触发的免疫(PTI)。转录组图谱显示，大多数OeSERK3同源基因在感病品种“Ogliarola salentina”中表达下调。在耐药的“Leccino”中，更多的OeSERK在对X.fitidiosa感染的反应中上调，我们推测一些OeSERK可能与PRRs起协同受体的作用。我们还建立了抗病和感病橄榄品种的愈伤组织和细胞悬浮培养，并探索了原型性PTI反应的特征以及转基因橄榄的产生，即转化EFR。我们的目标是回答两个关键问题：1.OeSERK如何调节PTI和对华支睾吸虫感染的反应？分析橄榄中的OeSERK并比较栽培品种将揭示接受功能分析的候选基因。OeSERK相互作用蛋白将在这两个品种中进行探索。2.与橄榄免疫和Xylella感染成功相关的PTI信号是什么？对一个抗性和感病橄榄品种的比较转录组图谱，以及评估对橄榄家族中一组免疫触发因子的原型PTI反应，可能会为这个问题提供见解。作为一种多年生木本植物和非模式植物，我们的总体目标是更好地了解橄榄的PTI，探索品种和家族的遗传多样性，用于PTI谱分析和与免疫相关的分子成分的鉴定。该项目完成后，将带来对橄榄免疫系统的新见解，并确定OeSERK和参与反应的相互作用者。了解免疫共受体的多样性对于控制敏感作物的抗性是至关重要的。

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.