Function of the Phytotoxin Coronatine in P. syringae DC3000/Plant Interactions

冠菌素（Coronatine，COR）是由植物病原细菌假单胞菌（Pseudomonaseryningae）产生的一种植物毒素。COR有助于P. pastingae的毒力;然而，COR的确切作用模式尚未确定。COR具有独特的结构，由两种不同的化合物组成：（1）冠酰胺酸（coronafacic acid，CFA）和（2）冠酰胺酸（coronamic acid，CMA）。CFA在结构上类似于茉莉酸（JA），茉莉酸是一种参与植物防御的植物激素，并作为这种内源性植物信号分子的分子模拟物发挥作用。CMA是氨基环丙基羧酸（ACC）的结构类似物，ACC是乙烯的直接前体，乙烯是另一种参与植物防御的内源植物激素。COR和植物防御信号（JA和ACC/乙烯）中涉及的化合物之间的结构和功能的相似性表明，COR可以通过干扰宿主防御反应和/或与植物中的其他生理过程来促进病原体的毒力。 此外，我们以前已经表明，COR是重要的早期定殖事件在宿主植物中，发现与抑制或调节宿主防御反应。 在拟议的工作中，一个遗传的方法，包括主机和病原体将被用来定义的作用，COR在拟南芥和番茄的发病机制。为此目的，PI和Co-PI已经开发了第一个明确定义的P. eriningae pv.的CFA-和CMA-突变体。番茄DC 3000是拟南芥和番茄的病原菌。PI和Co-PI实验室的独特专业知识和工具将用于整合宿主研究（COR如何调节敏感性？）与病原体（COR如何有助于毒力？）。具体而言，我们将：1）表征P.（2）利用CFA、CMA或两者同时缺失的突变体研究COR、CFA和CMA在拟南芥和番茄致病中的作用; 3）利用功能基因组学（微阵列研究）和DC 3000 COR-突变体，以研究COR、CFA和CMA在调节宿主细胞过程和防御反应中的作用;（4）分析COR、CFA和CMA对植物细胞生物学的影响，这些研究将有助于我们理解植物病害发生的机制。 通过利用我们可以同时研究病原体和植物宿主的系统，我们将能够识别和研究COR改变正常植物细胞过程的机制。 这些研究将提供深入了解COR功能在其他植物宿主的分子基础，一个贡献，可能会导致在农业和园艺系统中预防或控制植物病害的改进策略的发展。

Coronatine (COR) is a phytotoxin produced by the plant pathogenic bacterium Pseudomonas syringae. COR contributes to the virulence of P. syringae; however, a precise mode of action for COR has not been defined. COR has a unique structure consisting of two distinct compounds: (1) coronafacic acid (CFA), and (2) coronamic acid (CMA). CFA is structurally similar to jasmonic acid (JA), a plant hormone involved in plant defense, and functions as a molecular mimic of this endogenous plant signaling molecule. CMA is a structural analog of aminocyclopropyl carboxylic acid (ACC), the immediate precursor to ethylene, another endogenous plant hormone involved in plant defense. The structural and functional similarities between COR and compounds involved in plant defense signaling (JA and ACC/ethylene) suggest that COR may promote pathogen virulence by interfering with host defense responses and/or with other physiological processes in the plant. Furthermore, we have previously shown that COR is important for early colonization events in host plants, a finding consistent with the suppression or modulation of host defense responses. In the proposed work, a genetic approach that encompasses both host and pathogen will be used to define the role of COR in the pathogenesis of Arabidopsis and tomato. For this purpose, the PI and Co-PI have developed the first well-defined CFA- and CMA- mutants of P. syringae pv. tomato DC3000, a pathogen of Arabidopsis and tomato. The unique expertise and tools in the PI and Co-PI's laboratories will be used to integrate studies of the host (how does COR modulate susceptibility?) with the pathogen (how does COR contribute to virulence?). Specifically, we will: 1) characterize the COR genes in P. syringae pv. tomato strain DC3000 and study the structure and regulation of these genes; 2) investigate the role of COR, CFA and CMA in the pathogenesis of Arabidopsis and tomato by utilizing mutants deficient for production of CFA, CMA, or both molecules; 3) utilize functional genomics (microarray studies) and the DC3000 COR- mutants to investigate the role of COR, CFA, and CMA on modulating host cell processes and defense responses; and 4) analyze the effect of COR, CFA, and CMA on plant cell biology.These studies will contribute to our understanding of the mechanisms involved in disease development in plants. By taking advantage of a system where we can simultaneously study both the pathogen and plant host we will be able to identify and study the mechanisms by which COR alters normal plant cell processes. These studies will provide insight into the molecular basis of COR function in other plant hosts, a contribution that could result in the development of improved strategies for preventing or controlling plant disease in agricultural and horticultural systems.