Deciphering the molecular basis of organ-specificity in plant-microbe interactions

植物和病原体之间的共同进化最终形成了复杂的模式，其中病原体可以具有窄或宽的宿主范围。这种宿主特化的进化范式也适用于器官特异性感染过程。然而，为什么一些病原体喜欢特定的器官，而另一些病原体能够感染整个植物，这仍然是一个谜。研究表明，不同的植物器官可能利用不同的防御机制，但对病原体参与器官特异性的分子决定因素知之甚少。 由于其广泛的定殖不同宿主器官的能力， 马铃薯晚疫病病原体致病疫霉是一个完美的模型， 解决器官特异性。此外，虽然晚疫病抗性 育种往往集中在叶子，块茎抗性是一个同样重要的因素。 重要性状，因为块茎感染可导致严重产量 减少并促进次级软腐细菌的定植。 一些晚疫病抗性基因已被证明是无效的， 块茎，这可以解释为缺乏表达的 相应的无毒基因。 该建议旨在确定不同的效应互补物是否在不同的植物器官中起作用，并解释它们在决定器官特异性方面的贡献。候选器官特异性毒力因子将通过跨各种器官的效应子编码基因的转录组谱分析来鉴定，并使用功能测定来验证。预期器官特异性效应物在给定器官中相对于其他器官具有显著更高的表达水平，并且它们的毒力功能（例如抑制防御反应的能力）应以器官特异性方式起作用。与此同时，还将测试已知的无毒因子在来自遗传抗性马铃薯栽培品种的各种器官中引发防御反应的能力。 从基本的角度来看，器官特异性约束的阐明是植物-微生物相互作用的一个被忽视的组成部分，这对我们理解这种相互作用的进化和生态方面至关重要。此外，通过实施器官特异性与整株植物毒力和抗性机制的新知识，该研究计划将对农作物疾病控制新策略的发展产生实际影响。这将是一个前所未有的机会，将基础研究转化为作物改良战略，使加拿大产业受益。

Coevolution between plants and pathogens has culminated in intricate patterns where pathogens can have a narrow or wide host range. This evolutionary paradigm of host specialization also holds true for organ-specific infection processes. However, it remains elusive why some pathogens prefer a given organ, whereas others are able to infect the entire plant. Studies have shown that distinct plant organs may utilize distinct defense mechanisms, but not much is known about pathogens' molecular determinants involved in organ-specificity. Because of its broad ability to colonize different host organs, the potato late blight pathogen Phytophthora infestans is a perfect model to tackle organ-specificity. Moreover, while late blight resistance breeding has often focused on foliage, tuber resistance is an equally important trait since tuber infection can result in severe yield reduction and promotes colonization by secondary soft-rotting bacteria. Some late blight resistance genes have been shown to be ineffective in tubers, which could be explained by the absence of expression of the corresponding avirulence genes in these tissues. This proposal aims at identifying whether distinct effector complements act in various plant organs, and to decipher their contribution in dictating organ-specificity. Candidate organ-specific virulence factors will be identified by transcriptome profiling of effector-encoding genes across various organs and validated using functional assays. Organ-specific effectors are expected to possess a significantly higher expression level in a given organ relative to other organs and their virulence function (e.g. ability to suppress defense responses) should act in an organ-specific manner. In parallel, known avirulence factors will also be tested for their ability to trigger defense responses in various organs from genetically-resistant potato cultivars. From a fundamental point of view, the elucidation of organ-specific constraints is a neglected component of plant-microbe interactions that is crucial to our understanding of both evolutionary and ecological aspects of such interactions. Besides, by implementing novel knowledge on organ-specific vs. whole plant virulence and resistance mechanisms, this research program will have practical implications for the development of novel strategies for disease control in agricultural crops. This would represent an unprecedented opportunity to translate fundamental research into a crop improvement strategy that would benefit the Canadian industry.