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

植物和病原体之间的共同进化以错综复杂的模式达到顶峰，其中病原体可以有窄的或宽的寄主范围。这种宿主专门化的进化范式也适用于特定器官的感染过程。然而，为什么一些病原体偏爱特定的器官，而另一些病原体能够感染整个植物，这一点仍然难以捉摸。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。 由于其广泛的定植不同宿主器官的能力， 马铃薯晚疫病菌是防治马铃薯晚疫病的理想模式 解决器官特异性问题。此外，虽然抗晚疫病 育种往往集中在叶片上，块茎抗性同样也是 重要性状，因为块茎感染会导致严重的产量 减少和促进次级软腐菌的定植。 一些抗晚疫病基因已被证明是无效的 块茎，这可以解释为没有表达 这些组织中相应的无毒基因。 这一建议旨在确定不同的效应器补体是否在不同的植物器官中起作用，并破译它们在决定器官特异性方面的作用。候选的器官特异性毒力因子将通过对不同器官中的效应器编码基因的转录组图谱进行识别，并使用功能分析进行验证。器官特异性效应物在特定器官中的表达水平明显高于其他器官，它们的毒力功能(如抑制防御反应的能力)应该以器官特异性的方式发挥作用。同时，已知的无毒因子也将被测试它们在转基因马铃薯品种的不同器官中触发防御反应的能力。 从根本上讲，器官特异性限制的阐明是植物-微生物相互作用中被忽视的一个组成部分，对于我们理解这种相互作用的进化和生态方面都是至关重要的。此外，通过实施器官特定与整个植物毒力和抗性机制的新知识，该研究计划将对开发农业作物病害控制的新策略具有实际意义。这将是一个前所未有的机会，可以将基础研究转化为有利于加拿大工业的作物改良战略。

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.