Role of the Mai1 Protein Kinase in Connecting Host Recognition of Pathogen Effectors to MAPK Signaling

农作物病害给美国农业带来了严重的经济和环境挑战。这项研究的目标是产生有助于全面了解植物免疫系统的知识，并使创新的方法能够产生自然更能抵抗病原体的作物。这类植物将减少对化学农药的依赖，为农民带来经济利益，为美国消费者提供农药残留较少的食品，并将为美国农业的长期改善和可持续性做出贡献。该项目的重点是番茄与一种细菌病原体--丁香假单胞菌的相互作用。番茄，这会导致斑点病。这种植物与病原体的相互作用将被用来研究植物如何识别特定的病原体并激活它们的免疫系统，以减少疾病造成的损害。研究人员将培训一名博士后和一名研究生，学习用于研究植物-病原菌相互作用的尖端分子和生化方法。在我们对植物免疫的理解中，一个重要的悬而未决的问题是，通过抗病(R)蛋白识别病原体效应者是如何传递到有丝分裂原激活的蛋白激酶(MAPK)级联反应中的。这些级联由三个顺序激活的蛋白激酶(MAPKKK-MAPKK-MAPK)组成，在免疫相关的信号转导中发挥核心作用，最终导致局部细胞死亡和其他限制感染过程的防御反应。此前，MAPKKK(以下简称M3KA)被认为是免疫反应的积极调节因子。随后，具有四肽重复(TPR)结构域的蛋白激酶MAI1被发现是M3KA的相互作用因子。Mai1表达降低的植物不能激活免疫信号来响应三种R蛋白。在这个项目中，将使用多种实验方法来检验这一假设，即MAI1是R蛋白识别效应器和MAPK信号之间的分子桥梁。该项目的目标是：1)建立MAI1表达降低的植物，并表征MAI1对免疫的贡献；2)研究MAI1与免疫相关宿主蛋白的物理相互作用；3)表征翻译后修饰和TPR结构域在MAI1活性中的可能作用。MAI1为理解宿主对病原体效应器的识别如何传递到重要的免疫相关MAPK级联反应以及限制疾病的防御反应提供了一个切入点。这项拟议的研究将建立在一个众所周知的植物-病原体系统的基础上，以对植物中与免疫相关的信号转导的分子机制产生新的见解。

Diseases of crop plants pose serious economic and environmental challenges to U.S. agriculture. The goal of this research is to generate knowledge that contributes to a comprehensive understanding of the plant immune system and enable innovative methods for the generation of crop plants that are naturally more resistant to pathogens. Such plants will reduce dependence on chemical pesticides, produce economic benefits for farmers, provide food for U.S. consumers that has fewer pesticide residues, and will contribute to the long-term improvement and sustainability of U.S. agriculture. The project focuses on the interaction of tomato with a bacterial pathogen, Pseudomonas syringae pv. tomato, which results in speck disease. This plant-pathogen interaction will be used to investigate how plants recognize specific pathogens and activate their immune systems in order to decrease the damage caused by diseases. The investigator will train a postdoctoral associate and a graduate student in cutting-edge molecular and biochemical methods used for the study of plant-pathogen interactions.An important unanswered question in our understanding of plant immunity is how recognition of pathogen effectors by disease resistance (R) proteins is transmitted to mitogen-activated protein kinase (MAPK) cascades. These cascades consist of three sequentially activated protein kinases (MAPKKK-MAPKK-MAPK) and play a central role in immunity-related signal transduction leading ultimately to localized cell death and other defense responses that limit the infection process. A MAPKKK (hereafter M3Ka) was identified previously as a positive regulator of the immune response. Subsequently Mai1, a protein kinase with a tetratricopeptide repeat (TPR) domain, was discovered to be an interactor of M3Ka. Plants with reduced expression of Mai1 are unable to activate immune signaling in response to three R proteins. In this project multiple experimental approaches will be used to test the hypothesis that Mai1 is a molecular bridge between recognition of effectors by R proteins and MAPK signaling. The project objectives are to: 1) Develop plants with reduced expression of Mai1 and characterize the contribution of Mai1 to immunity; 2) Investigate the physical interaction of Mai1 with immunity-associated host proteins; 3) Characterize the possible role of post-translational modifications and the TPR domain in Mai1 activity. Mai1 provides an entry point into understanding how host recognition of pathogen effectors is transmitted to an important immunity-associated MAPK cascade and on to defense responses that limit disease. The proposed research will build on a well-understood plant-pathogen system to generate new insights into the molecular mechanisms underlying immunity-associated signal transduction in plants.