Coordination of Plant Growth and Defense Through Key Regulators in Salicylic Acid and Brassinosteroid Pathways

在自然环境中，植物可以被许多病原体感染，包括真菌、细菌、卵菌、病毒和线虫。因此，强健的免疫系统是植物生存的先决条件。不幸的是，当植物将能量分配给防御而不是生长时，就会产生适应性成本，这将损害植物的生长，导致作物产量损失。植物防御激素水杨酸（SA）在植物防御许多病原体中起着重要作用。相比之下，内源激素油菜素内酯（BRs）调节植物正常生长发育所需的多种生理过程。植物已经发展出复杂的策略来协调生长和免疫，但我们对潜在机制的理解仍然有限。本项目旨在通过BR和SA通路中关键调控因子之间的相互作用，揭示植物生长和防御协调的基本机制。这些研究将极大地增加对植物如何在分子水平上实现平衡生长和防御的理解，并将最终有助于开发有效和新颖的策略来控制作物病害，而不会造成重大的产量损失。本项目资金将用于培训初高中学生和教师在柑橘树出现明显症状之前早期发现柑橘绿色病。通过将分子技术与现实生活中的紧迫问题联系起来，我们的项目将展示植物科学的重要性，并激励学生成为下一代领先的植物科学家。植物利用病原体相关分子模式（PAMP）触发免疫（PTI）和效应触发免疫（ETI）两层监测系统来识别入侵的病原体。在被病原体局部感染后，植物可以在整个植物中激活更强、更快的防御反应，以抵御随后广泛的病原体感染。这种现象被称为系统性获得性耐药性（SAR）。早期研究表明，EDS1和NPR1是sa介导的植物防御的两个中心枢纽，而BZR1和BES1是植物生长激素BR信号传导的两个关键转录因子。本项目主要研究植物如何通过BR和SA之间的串扰优化生长和防御。初步数据表明，EDS1和NPR1都与BES1相互作用，而EDS1也与BZR1存在物理关联。已发表的数据表明，SA、NPR1和EDS1抑制下胚轴伸长，而BZR1调节ETI。本项目的第一个目标是研究BZR1和BES1是否以及如何通过与EDS1和NPR1的相互作用影响PTI。第二个目标是确定BZR1和BES1是否以及如何通过影响EDS1和NPR1的功能来影响ETI和系统植物免疫。最终目的是阐明EDS1和NPR1在sa介导的植物生长抑制中的作用，通过它们与BR通路中关键调节因子的物理关联。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。

In their natural environments, plants can be infected by many pathogens including fungi, bacteria, oomycetes, viruses, and nematodes. Therefore, a robust immune system is a prerequisite for the survival of plants. Unfortunately, when plants allocate energy for defense instead of growth, there is a fitness cost, which will compromise plant growth, resulting crop yield loss. The plant defense hormone salicylic acid (SA) plays an essential role in plant defense against many pathogens. In contrast, the endogenous hormones called brassinosteroids (BRs) regulate multiple physiological processes required for normal plant growth and development. Plants have developed sophisticated strategies to coordinate growth and immunity, but our understanding of the underlying mechanisms remains limited. This project aims to unravel fundamental mechanisms of plant growth and defense coordination through interactions between key regulators in BR and SA pathways. These studies will greatly increase the understanding of how plants achieve balanced growth and defense at the molecular level and will ultimately contribute to the development of effective and novel strategies to control crop diseases without significant yield loss. Funding from this project will be used to train middle and high students and teachers on detecting citrus greening disease at early stages before the citrus trees show any obvious symptoms. By connecting molecular technology with urgent real-life problems, our program will showcase the importance of plant science and inspire students to become the next generation of leading plant scientists. Plants deploy a two-tiered surveillance system, which includes pathogen-associated molecular pattern (PAMP)-triggered immunity (PTI) and effector-triggered immunity (ETI), to recognize invading pathogens. After a local infection by a pathogen, plants can activate stronger and faster defense responses in the entire plant against later infections by a broad spectrum of pathogens. This phenomenon is termed systemic acquired resistance (SAR). Early studies have demonstrated that EDS1 and NPR1 function as two central hubs in SA-mediated plant defense, while BZR1 and BES1 act as two key transcription factors in the plant growth hormone BR signaling. This project focuses on investigating how plants optimize growth and defense through the crosstalk between BR and SA. The preliminary data have shown that both EDS1 and NPR1 interact with BES1, while EDS1 is also physically associated with BZR1. The published data demonstrated that SA, NPR1, and EDS1 inhibit hypocotyl elongation, while BZR1 regulates ETI. The first objective of this project is to study whether and how BZR1 and BES1 influence PTI through interacting with EDS1 and NPR1. The second objective is to determine if and how BZR1 and BES1 impact ETI and systemic plant immunity by affecting the functions of EDS1 and NPR1. The final objective is to elucidate the roles of EDS1 and NPR1 in SA-mediated plant growth inhibition through their physical associations with key regulators in the BR pathway.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.