Molecular mechanisms that boost systemic immunity in plants

植物是缺乏循环免疫细胞的无根生物。为了对抗细菌感染，植物利用小的、可移动的代谢物在它们的血管系统中传播，在受到攻击的部位和整个植物体内开启防御。通过激活未感染组织中的防御，植物处于一种高度免疫状态，限制了新的病原体感染。这种免疫反应被称为防御启动或全身获得性抵抗。最近的研究发现了一种被称为n -羟基胡椒酸（NHP）的氨基酸衍生物，它是开启防御启动所需的生物活性代谢物。关于NHP如何影响植物防御和发育的信息很少。值得注意的是，用NHP浇灌或注射植物足以诱导防御启动并防止细菌和真菌感染。这些发现表明，改变植物体内的NHP水平或向植物提供NHP以增强其防御反应可能是提高农业和园艺植物抗病能力的有效策略。该项目将研究NHP生物学的重要方面。关键问题包括：(1)NHP防御信号持续多久？(2)防御信号是如何关闭的？(3) NHP信号如何影响正常的生长发育？病原体是否操纵NHP生物学来关闭这种植物防御系统？这些问题将通过化学生物学和功能基因组学的方法来回答。长期目标是研究可能的化学应用和/或工程努力，以增强植物的防御启动，以改善植物健康。这项研究将在研究生、本科生和高中各级提供密集的研究训练，并特别考虑到妇女、代表性不足的少数民族和来自资源不足背景的人。研究和推广活动还将为斯坦福大学的研究生和研究生提供实践教学和指导培训。系统性获得性抗性（SAR）是一种全球性的植物免疫反应，在病原体感染部位诱导，在整个植物中引发持久的广谱抗病性。即使在没有初始感染的情况下，单一的小代谢物n -羟基-黑果酸（NHP）对于启动这种增强的免疫状态也是必要和充分的。有趣的是，NHP及其衍生物似乎是可移动的代谢物，阐明了在植物体内长距离启动和扩大防御反应所需的信号的化学性质。此外，仅在局部组织中过度表达NHP生物合成途径可以保护远端组织免受病原体感染。因此，这些数据强调了将化学或代谢工程方法转化为在病原体压力下启动和/或增强疾病抗性的有趣可能性。目前，关于NHP生物合成的调控、NHP信号传导的动力学以及该防御启动机制对植物生长和健康的普遍影响等方面的信息较少。本研究的目的是阐明NHP化学防御的时间动态及其在天然和工程条件下保护重要作物植物的有效性。本研究将验证一个假设，即NHP生物合成的调节和NHP生物活性信号的持续时间可以通过滴定来提高抗病性，而不会影响植物的适应性。模式蔬菜番茄，茄，将用于阐明NHP的基本方面。这项研究将为NHP信号传导和与NHP生产改变相关的生长防御的动力学提供见解。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 sessile organisms that lack circulating immune cells. To fight bacterial infections, plants use small, mobile metabolites that travel throughout their vascular system to turn on defenses at sites of attack and throughout the plant body. By activating defenses in uninfected tissues, plants exist in a heightened immune state that limits new pathogen infections. This immune response is known as defense priming or systemic acquired resistance. Recent research identified an amino acid derivative called N-hydroxy-pipecolic acid (NHP) that is the bioactive metabolite required to turn on defense priming. There is sparse information for how NHP affects plant defense and development. Notably, watering or injecting plants with NHP is sufficient to induce defense priming and protect against bacterial and fungal infections. These findings suggest that altering NHP levels in plants or providing NHP to plants to enhance their defense responses may be effective strategies to enhance disease resistance in plants used in agriculture and horticulture. This project will study important aspects of NHP biology. Key questions include: (1) How long does the NHP defense signal last? (2) How is the defense signal turned off? (3) How does NHP signaling impact normal growth and development? (5) Do pathogens manipulate NHP biology to turn off this plant defense system? These questions will be answered by using chemical biology and functional genomic approaches with tomato, an important crop plant. The long-term goal is to investigate possible chemical applications and/or engineering efforts to enhance defense priming in plants to improve plant health. This study will provide intensive research training at the graduate, undergraduate and high school level with special consideration of women, underrepresented minorities, and those from under-resourced backgrounds. The research and outreach activities will also provide hands-on teaching and mentorship training for Stanford graduate and postgraduate students. Systemic acquired resistance (SAR) is a global plant immune response induced at the site of pathogen infection that triggers long-lasting and broad-spectrum disease resistance throughout the plant. A single small metabolite, N-hydroxy-pipecolic acid (NHP), is necessary and sufficient for initiation of this heightened immune state, even in the absence of an initial infection. Interestingly, NHP and its derivatives appear to be mobile metabolites, illuminating the chemical nature of the signals that are required to initiate and amplify defense responses over long distances within the plant body. Moreover, overexpression of the NHP biosynthetic pathway in local tissues alone can protect distal tissues from pathogen infection. These data thus highlight the intriguing possibility for translating a chemical or metabolic engineering approach to prime and/or enhance disease resistance under pathogen pressure. Currently, there is sparse information available regarding the regulation of NHP biosynthesis, dynamics of NHP signaling, and universal impact of this defense priming mechanism on plant growth and health. The goal of this research is to elucidate the temporal dynamics of NHP chemical defense and its effectiveness in protecting important crop plants under native and engineered conditions. This study will test the hypothesis that the regulation of NHP biosynthesis and the duration of the NHP bioactive signal can be titrated to increase disease resistance without compromising plant fitness. The model vegetable tomato, Solanum lycopersicum, will be used to elucidate fundamental aspects of NHP. This research will provide insight to the dynamics of NHP signaling and growth-defense associated with altered NHP production.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.