Deciphering the guard cell metabolome in plant pathogen defense

农作物不断受到细菌性病原体的挑战，每年造成产量和经济价值的巨大损失。病原体通过伤口和叶片表面的小孔进入植物体内。这些孔被称为气孔，由高度特化的保护细胞形成。由保卫细胞介导的气孔开放允许二氧化碳的吸收。吸收后，二氧化碳被光合作用捕获，产生碳水化合物等有机物质；因此，气孔打开对农业产量和生物能源生产至关重要。然而，开放的气孔也允许水蒸气流失，并为病原体创造入口，这是植物的责任。众所周知，当防御细胞感知到病原体时，它们会在一小时内关闭气孔作为免疫反应。然而，随后，气孔再次打开，病原体进入。本项目旨在阐明在病原菌感染过程中，脂质和脂肪酸在调节气孔关闭和打开中的作用。这项研究将使科学家们深入了解对病原体触发的气孔关闭和打开重要的保护细胞脂质代谢物。该研究结果具有广泛的社会影响，例如为合理的作物育种提供信息，以提高病原体防御和作物产量。研究结果将通过社区知识库和免费出版物（例如Metabolight， The Plant Journal）向公众提供。该项目还将能够对不同级别的学生，包括妇女和代表性不足的学生进行跨学科培训。培养下一代科学家和公民对社会和世界具有深远的积极影响。Chen实验室观察到，在使用由鞭毛蛋白n端22氨基酸肽（flg22）组成的细菌激发子治疗后，保护细胞的脂质代谢物发生了显著变化。Assmann实验室先前已经证明了脂质代谢物鞘氨醇-1-磷酸（S1P）作为脱落酸信号传导的一个组成部分的作用。然而，S1P和其他脂质和脂肪酸在气孔免疫中对注射器假单胞菌pv的作用。番茄（Pst DC3000）是未知的。这里的假设是脂质代谢物作为保护细胞病原体信号传导的重要调节剂起作用。目的是：1)确定Pst DC3000触发气孔运动过程中保护细胞中脂质和脂肪酸的动态变化；2)通过脂质组学分析，确定Pst DC3000在脂质生物合成和代谢相关突变体中触发的气孔运动，并表征脂质代谢物作为信号分子在触发气孔运动中的作用。使用的方法包括脂质组学、细胞生物学、遗传学和生物化学。本课题重点研究脂质和脂肪酸在Pst DC3000的气孔免疫中的作用。研究结果有望揭示新的脂质代谢物功能，促进对气孔免疫分子机制的理解，并说明包括脂质组学在内的综合方法在揭示新的生物机制方面的力量。该奖项反映了美国国家科学基金会的法定使命，并通过基金会的智力价值和更广泛的影响审查标准进行了评估，认为值得支持。

Crops are constantly challenged by bacterial pathogens, which cause huge losses in yield and economical value every year. The pathogens enter the plant body through wounds and through tiny pores on leaf surfaces. These pores are called stomata, and are formed by highly specialized cells called guard cells. Stomatal opening mediated by the guard cells allows carbon dioxide uptake. After uptake, carbon dioxide is captured by photosynthesis, generating organic materials such as carbohydrates; therefore stomatal opening is critical for agricultural yield and bioenergy production. However, the open stomatal pores also allow water vapor loss, and create entries for pathogens, which are liabilities for plants. It is known that when guard cells sense pathogens, they close stomata within an hour as an immune response. However, subsequently, the stomata open again and pathogens go in. This project aims to elucidate how lipids and fatty acids function in regulating the stomatal closure and opening during pathogen infection. This research will enable scientists to gain an in-depth understanding of guard cell lipid metabolites important for pathogen triggered stomatal closing and opening. The outcome of the research has broad societal impact, e.g., for informing rational crop breeding to enhance pathogen defense and crop yield. The results will be made available to the public via community repositories and no-cost publications (e.g. Metabolight, the Plant Journal). The project will also enable cross-disciplinary training of students at different levels, including women and under-represented students. Training the next generation of scientists and citizens has far-reaching positive impacts for society and the world.The Chen lab has observed significant lipid metabolite changes in guard cells in response to treatment with a bacterial elicitor comprised of the flagellin N-terminal 22 amino acid peptide (flg22). The Assmann lab has previously demonstrated the effect of the lipid metabolite sphingosine-1-phosphate (S1P) as a component of abscisic acid signaling. However, the roles of S1P and other lipids and fatty acids in stomatal immunity against Pseudomonas syringe pv. tomatao (Pst DC3000) are not known. Here the hypothesis is that lipid metabolites function as important regulators of guard cell pathogen signaling. The goals are to: 1) determine dynamic changes of lipids and fatty acids in guard cells during Pst DC3000 triggered stomatal movement; 2) determine stomatal movement triggered by Pst DC3000 in relevant mutants of lipid biosynthesis and metabolism implicated from the lipidomics analyses, and characterize the effects of lipid metabolites as signaling molecules in triggering stomatal movement. Approaches to be used include lipidomics, cell biology, genetics and biochemistry. This focused project specially targets the functions of lipids and fatty acids in stomatal immunity against Pst DC3000. The results are expected to reveal novel lipid metabolite functions, boost understanding of molecular mechanisms that underlie stomatal immunity, and illustrate the power of integrated approaches involving lipidomics to reveal novel biological mechanismsThis 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.