EAGER: Characterization of a putative Xanthomonas-Pseudomonas disease complex of Cotton

在农业环境中，植物是复杂微生物群落的宿主。在这些群落中，竞争是常见的，因为不同的微生物争夺有限的营养供应，但也有合作的机会。在定义寄主-病原体相互作用的“军备竞赛”的背景下，病原体-病原体协作代表了一种潜在的强大机制，使疾病生物体克服寄主抗性策略，对农业具有严重影响。例如，2001年，棉花白叶枯病(CBB)在美国南部重新出现，这是一种有抗药性的棉花品种。令人惊讶的是，在抗CBB的棉花植株上观察到了这种疾病。更仔细的检查发现，在这些病棉上发现了CBB病原菌和第二种细菌病原菌。这种共同出现导致了这样的假设，即这两种细菌病原体正在合作抑制宿主抵抗反应并导致疾病。这个项目使用基因组学和分子生物学的方法来检验这一假设。如果得到证实，这项研究将揭示克服寄主抗性的病原菌策略的新前沿，这将是未来需要考虑的。CBB由柑橘黄单胞菌PV引起。麦芽糖(Xcm)。从抗Xcm的棉花植株上共分离到Xcm和另一种病原菌--丁香假单胞菌(Pseudomonas Syringae)。因此，Xcm和Ps可能正在形成一种疾病复合体，抑制Xcm引发的抗性。本研究旨在揭示XCM与Ps之间可能的协作机制(S)。第一个目标是建立实验系统和分析方法，改编自经典的植物病理学技术，以仔细定义Xcm和Ps之间的潜在相互作用点。第二个目标是寻找Xcm和Ps之间潜在的合作分子机制。例如，Ps可以使用其III型效应器来抑制通常由Xcm触发的抵抗反应。这一假说将通过比较接种Xcm、Ps以及与Xcm和Ps共接种后植物防御基因的表达来验证。RNA测序和差异基因表达分析将揭示这两种病原菌使用的相关毒力机制和棉花内部触发的反应。最终目标将通过在XCM和/或Ps中构建基因敲除并进行致病性测试，直接测试特定细菌基因在任何相互作用中的作用。该项目通过考虑多种细菌植物病原体同时攻击同一寄主的影响，开辟了重要的新领域。了解定义这些复杂相互作用的规则是满足不断增长的人口和不断变化的环境的农业需求所必需的。该奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

In agricultural settings, plants are hosts to complex microbial communities. Competition is common within these communities as diverse microbes compete for a limited supply of nutrients, but there are also opportunities for collaboration. In the context of the "arms race" that defines host-pathogen interactions, pathogen-pathogen collaboration represents a potentially powerful mechanism for disease organisms to overcome host resistance strategies, with severe implications for agriculture. As an example, in 2001, cotton bacterial blight (CBB), a disease for which there are resistant cotton varieties, re-emerged across the southern USA. Surprisingly, the disease was observed on CBB-resistant cotton plants. Closer examination revealed the CBB pathogen as well as a second bacterial pathogen on these diseased cotton plants. The co-occurrence led to the hypothesis that the two bacterial pathogens are collaborating to suppress host resistance responses and cause disease. This project tests that hypothesis using genomics and molecular biology approaches. If confirmed, this research will have revealed a new frontier of pathogen strategies to overcome host resistance that will need to be considered in the future.CBB is caused by Xanthomonas citri pv. malvacearum (Xcm). Xcm and a second pathogen, Pseudomonas syringae (Ps), were co-isolated from cotton plants that are resistant to Xcm. Xcm and Ps may, therefore, be forming a disease complex that suppresses the resistance triggered by Xcm. This research aims to reveal the putative mechanism(s) of collaboration between Xcm and Ps. The first aim will establish experimental systems and assays, adapted from classic plant pathology techniques, to carefully define points of potential interaction between Xcm and Ps. The second aim will seek potential molecular mechanisms of collaboration between Xcm and Ps. For example, Ps may use its repertoire of type III effectors to repress the resistance response normally triggered by Xcm. This hypothesis will be tested by comparing plant defense gene expression after inoculation with Xcm, Ps and co-inoculation with Xcm and Ps. RNA sequencing and differential gene expression analyses will reveal the relevant virulence mechanisms employed by both pathogens and the response triggered within cotton. The final aim will directly test the roles of specific bacterial genes in any interaction by constructing genetic knockouts in Xcm and/or Ps and conducting pathogenicity assays. This project breaks important new ground by considering the effect of multiple bacterial plant pathogens attacking the same host simultaneously. Understanding the rules that define these complex interactions is required to meet the agricultural needs of an increasing population and changing environment.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.