CAREER:Exploring apoplastic sulfate restriction and stress response mis-regulation as major mechanisms of pattern-triggered immune action on bacteria

植物不断受到入侵微生物的挑战。为了对抗这些入侵者，植物部署了一个强大而有效的免疫系统，能够检测、适当地响应和限制大多数微生物的增殖。虽然人们对微生物检测的分子机制和与免疫诱导相关的信号传导机制的了解越来越详细，但免疫功能限制微生物增殖的分子机制一直难以捉摸。该项目的长期目标是了解植物免疫作用所针对的细菌机制。免疫激活的植物似乎限制了可利用的硫，这是生命的基本元素，从而阻止了细菌的增殖。植物免疫也会干扰细菌对压力的保守反应，导致细菌对免疫输出的敏感性增加。描述这些潜在的免疫作用模式将对我们对植物免疫的理解具有广泛的意义，并为植物病害管理提供新的靶点和实用策略。该项目的广泛教育目标包括提高研究生在植物病理学方面的能力，向所有背景的学生（包括非科学专业的学生）教授植物和植物病害科学，并通过探究性学习增强对科学的理解。该项目的更广泛影响扩大了公众对植物病害的认识，并可能提出新的作物保护解决方案。模式触发免疫（Pattern Triggered Immunity， PTI）是植物抵御病原菌入侵的第一道诱导免疫防线，由宿主对保守的微生物相关分子模式的识别驱动。PTI在限制微生物不受控制的生长方面起着关键作用。然而，PTI限制多种微生物生长的机制尚不清楚。细菌病原体对PTI的转录反应是本项目关注PTI限制病原体生长的作用机制的基础。利用植物遗传学、正向和反向细菌遗传学、化学和蛋白质分析以及细菌转录组学，本项目将测试以下假设：1)在PTI过程中，外质体硫酸固存限制细菌增殖；2) PTI输出干扰AlgU细菌应激反应级联的激活，导致细菌对免疫相关应激源的敏感性增加；3)尽管PTI输出是多方面的和半冗余的，但细菌对PTI的反应可用于描述和连接特定输出到植物防御网络的部门。该项目包括旨在提高公众对植物疾病和免疫的认识的教育活动，并将重点放在对非专业学生的教育上。这些目标将通过开发两门以探究为基础的本科学习课程来实现，这些课程包含植物疾病农业生物技术概念，针对非科学专业的学生，并通过为佐治亚州雅典-克拉克县中学的教师试行同行指导的、以探究为基础的植物-微生物相互作用课程计划。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Plants are constantly challenged by invading microbes. To counter these invaders, plants deploy a robust and effective immune system capable of detecting, appropriately responding to and restricting the proliferation of most microbes. While the molecular mechanisms underlying the detection of microbes and the signaling mechanisms associated with the induction of immunity are understood in ever increasing detail, the molecular mechanism(s) by which microbial proliferation is restricted by immune functions have been elusive. The long-term goal of this project is to understand the bacterial mechanisms targeted by plant immune action. Immune-activated plants appear to limit available sulfur, an essential element for life, thus blocking bacterial proliferation. Plant immunity also interferes with conserved bacterial responses to stress, resulting in the increased sensitization of bacteria to immune outputs. Characterizing these potential modes of immune action will have broad implications for our understanding of plant immunity and provide new targets and practical strategies to manage plant diseases. The project's broad educational goals include increasing pre-graduate competency in plant pathology, teaching plant and plant disease science to students from all backgrounds, including non-science majors, and enhancing scientific understanding through inquiry-based learning. The project's broader impacts expand public knowledge of plant diseases and may suggest new crop protection solutions. Driven by host recognition of conserved microbe-associated molecular patterns, Pattern Triggered Immunity (PTI) is the first line of induced immune defenses used by plants against invading pathogens. PTI plays a key role in restricting the unchecked growth of microbes. However, the mechanisms by which PTI restricts the growth of broad classes of microbes are unclear. The transcriptional response of bacterial pathogens to PTI is the basis for this project's focus on mechanisms of PTI action that restrict pathogen growth. Deploying plant genetics, forward and reverse bacterial genetics, chemical and protein analysis, and bacterial transcriptomics, this CAREER project will test the following hypotheses: 1) Apoplastic sulfate sequestration restricts bacterial proliferation during PTI; 2) PTI outputs interfere with activation of the AlgU bacterial stress response cascade, resulting in increased bacterial sensitization to immune-associated stressors; and 3) although PTI outputs are multifaceted and semi-redundant, bacterial responses to PTI can be used to delineate and link specific outputs to sectors of the plant defense network. This project incorporates educational activities aimed at raising public knowledge about plant diseases and immunity and will focus on the education of non-specialist students. These goals will be achieved by the development of two undergraduate inquiry-based learning courses incorporating plant disease agricultural biotechnology concepts and targeted towards non-science majors, and by piloting peer-mentored, inquiry-based learning lesson plans about plant-microbe interactions for teachers in Athens-Clarke County, Georgia, middle schools.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.