The Contribution of Phytophthora effectors to host range and non-host resistance

世界人口的不断增长和气候变化的影响对世界粮食供应提出了更高的要求。全球粮食安全的一个主要制约因素是植物病虫害造成的作物损失。随着批准用于农业的化学品的条件越来越严格，在不久的将来，有效的杀真菌剂和杀虫剂的选择将变得更加有限。此外，由于渗入的宿主抗性基因在田间被病原体和害虫迅速击败，迫切需要探索持久的疾病和害虫抗性来源，并将提供长期的粮食安全。植物面临着不断的害虫和微生物威胁，并通过采用至少两层诱导防御反应来保护自己。第一层涉及通过细胞表面模式识别受体（PRR）识别病原体相关分子模式（PAMP）以安装PAMP触发的免疫（PTI）。成功的（适应的）病原体在宿主细胞内分泌和递送分子，效应物，以抑制这些防御。第二层防御涉及免疫受体或NB-LRR蛋白识别效应子，以引起效应子触发的免疫（ETI）。这种识别通常基于NB-LRR检测效应子靶向的宿主蛋白质的构象/生物化学状态的变化。大多数植物对大多数病原体都具有抗性，这被称为非宿主抗性（NHR）。根据定义，这对病原体物种的所有遗传变体都有效，因此持久。NB-LRR蛋白的效应子识别被认为是与病原体的天然宿主密切相关的植物物种中NHR的主要决定因素。相比之下，存在证据表明，与病原体的天然宿主有远亲关系的植物物种中的诱导型NHR是效应子不能适当靶向植物蛋白并抑制免疫的结果。植物病原菌效应子及其靶蛋白的鉴定为研究这些蛋白在非寄主抗性中的作用开辟了新的途径，旨在对效应子及其靶蛋白和NB-LRR蛋白在茄科植物非寄主抗性中的作用有一个关键的认识。茄科包括经济上重要的粮食作物，如辣椒、番茄和马铃薯，后者是世界第四大粮食作物，在欧洲仅次于小麦。我们将利用来自具有不同宿主范围的2种重要茄科病原体的效应子集：卵菌Phytophthora infestans（感染马铃薯和番茄但不感染辣椒）和P. capsici（感染辣椒和番茄但不感染马铃薯）。我们将评估疫霉效应子对确定宿主范围的贡献。我们的主要目标是（i）评估效应子是否在非宿主茄科植物中触发NB-LRR介导的免疫，以及（ii）拟南芥中的诱导型NHR是否构成效应子未能修饰预期靶标从而抑制PTI。我们将利用马铃薯、番茄、N. benthamiana，N.樟子松和辣椒以鉴定致病疫霉和辣椒疫霉效应子的靶标。然后，我们将能够调查他们的作用，在非寄主茄科plants.The拟议的工作将揭示NB-LRR的贡献，和他们监测的效应靶，茄科作物NHR。我们将建立一个必要的平台，确定NHR的分子基础，识别激活NHR的关键效应子，并为靶向搜索相关基因铺平道路。此外，我们将确定拟南芥PTI调节组件，不敏感的效应活性，可以部署在茄科作物。这种方法将建立一个高度持久的感染屏障。

An increasing world population and impacts of climate change place ever-greater demands on the world food supply. A major constraint to global food security is crop loss due to plant pests and diseases. With the increasing stringency of conditions under which chemicals are approved for agriculture, the choice of effective fungicides and pesticides will become more limited in the near future. Furthermore, as introgressed host resistance genes are rapidly defeated by pathogens and pests in the field, there is an urgent need to explore sources of disease and pest resistance that are durable and will provide long term food security.Plants face a constant barrage of pest and microbial threats and defend themselves by employing at least two layers of inducible defence responses. The first layer involves recognition of Pathogen-Associated-Molecular-Patterns (PAMPs) by cell surface pattern recognition receptors (PRRs) to mount PAMP-triggered immunity (PTI). Successful (adapted) pathogens secrete and deliver molecules, effectors, inside host cells to suppress these defences. The second defence layer involves recognition of effectors by immune receptors, or NB-LRR proteins, to evoke effector-triggered immunity (ETI). This recognition is often based on detection of changes by NB-LRRs in the conformational/biochemical state of host proteins that are targeted by effectors. Most plants are resistant to most pathogens, which is termed non-host resistance (NHR). By definition this is effective against all genetic variants of a pathogen species, and thus durable. Effector recognition by NB-LRR proteins has been proposed to be a major determinant of NHR in plant species that are closely related to the pathogens' natural hosts. In contrast, evidence exists that inducible NHR in plant species that are distantly related to the pathogen's natural host(s) is the result of the inability of effectors to appropriately target plant proteins and suppress immunity. Recent progress in the identification of plant pathogen effectors, and their targets, has opened new avenues to investigate the contributions of these proteins to determining non-host resistance.This proposal aims to generate a key understanding of the role of effectors, their targets, and NB-LRR proteins in non-host resistance in the Solanaceae. The Solanaceae include economically important food crops, such as pepper, tomato, and potato, the latter being the world's fourth largest food crop, and the second largest in Europe after wheat. We will exploit effector sets from 2 important solanaceous pathogens with differing host ranges: the oomycetes Phytophthora infestans (infects potato and tomato but not pepper) and P. capsici (infects pepper and tomato but not potato). We will assess the contribution of Phytophthora effectors to defining host range. Our key objectives are to (i) assess whether effectors trigger NB-LRR-mediated immunity in non-host solanaceous plants, and (ii) whether inducible NHR in Arabidopsis, constitutes a failure of effectors to modify intended targets and thus suppress PTI. We will exploit the genome sequences of potato, tomato, N. benthamiana, N. sylvestris and pepper to identify targets for P. infestans and P. capsici effectors. We will then be able to investigate their role in mediating effector recognition in non-host solanaceous plants.The proposed work will shed light on the contribution of NB-LRRs, and the effector targets they monitor, to NHR within solanaceous crops. We will establish an essential platform that determines the molecular basis of NHR, identifies the critical effectors that activate NHR and paves the way to targeted searches for associated genes. Moreover, we will identify Arabidopsis PTI regulatory components, insensitive to effector activity, that can be deployed in Solanaceous crops. This approach will build a highly durable barrier to infection.