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

作物病害对美国农业构成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，并使创新方法能够产生对病原体具有天然抗性的作物。这些工厂将减少对化学农药的依赖，为农民带来经济效益，为美国消费者提供农药残留较少的食品，并将有助于美国农业的长期改善和可持续性。该项目的重点是番茄与细菌病原体，假单胞菌pv。番茄，导致斑点病。这种植物-病原体相互作用将用于研究植物如何识别特定的病原体并激活其免疫系统，以减少疾病造成的损害。研究人员将培训一名博士后助理和一名研究生，用于研究植物-病原体相互作用的尖端分子和生物化学方法。在我们对植物免疫的理解中，一个重要的未回答的问题是抗病（R）蛋白对病原体效应子的识别如何传递到丝裂原活化蛋白激酶（MAPK）级联。这些级联反应由三种顺序激活的蛋白激酶（MAPKKK-MAPKK-MAPK）组成，并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限制感染过程的其他防御反应。MAPKKK（以下称为M3 Ka）先前被鉴定为免疫应答的正调节剂。随后发现Mai 1是一种具有三肽重复序列（TPR）结构域的蛋白激酶，其与M3 Ka相互作用。Mai 1表达减少的植物不能激活响应三种R蛋白的免疫信号传导。在本项目中，将使用多种实验方法来验证Mai 1是R蛋白识别效应子和MAPK信号传导之间的分子桥梁的假设。该项目的目标是：1）开发Mai 1表达减少的植物并表征Mai 1对免疫的贡献; 2）研究Mai 1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Mai 1活性中的可能作用。Mai 1提供了一个切入点，可以了解宿主对病原体效应物的识别如何传递到重要的免疫相关MAPK级联反应，并传递到限制疾病的防御反应。拟议的研究将建立在一个众所周知的植物病原体系统，以产生新的见解的分子机制，免疫相关的信号转导在植物中。

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.