Regulation and Assembly of a Type III Protein Secretion Apparatus in Pseudomonas syringae

Hutcheson 9729524 III型蛋白质分泌系统是许多哺乳动物和植物病原细菌的致病性所必需的。这种类型的分泌系统与蛋白质从细菌转移到宿主的靶细胞中有关。我们以前已经表明，从假单胞菌Pss 61分离的hrp/hrmA基因簇编码一个假定的III型蛋白质输出装置（PEA）的保守组件，以及一个明显专用的监管系统，涉及HrpL。因此，P. pestingae的致病作用可能涉及细菌对植物细胞的粘附、植物细胞对hrp基因表达的接触依赖性诱导、hrp编码的III型PEA的组装以及毒力和宿主范围决定因子到靶植物细胞中的易位。到目前为止，用于协调PEA组装的机制仅被部分表征。本项目的总体目标是阐明控制hrp编码的PEA组装的机制，并确定PEA在P. erythingae菌株致病性中的作用。本实验将完成HrpL依赖性调控系统的表征; 2）利用新型报告基因系统研究Avr产物的分泌途径; 3）利用遗传筛选技术鉴定HrpL相关调控系统调控的遗传决定簇。 植物有能力识别和应对入侵的病原体，以保护自己，从而最大限度地减少疾病。这涉及植物细胞对病原体信号的识别。 已经证明假单胞菌的hrp基因在识别过程中起作用，并且预测这些细菌基因的产物形成将蛋白质注入植物细胞的装置。 这些注入的蛋白质是植物细胞响应的刺激物。 这些实验将使用遗传方法来研究识别过程的早期步骤。 阐明hrp编码的分泌器的调控和功能将对植物-微生物分子相互作用的研究产生重要影响，它将为植物抗病性的调控分子和调控途径，细菌致病性的内在机制，植物与微生物相互作用的研究提供新的思路。3）通过针对病原体的特定属性培育针对广泛病原体的稳定作物抗性的新策略; 4）哺乳动物和植物病原体致病性中蛋白分泌系统的进化。

Hutcheson 9729524 Type III protein secretion systems are required for the pathogenicity of many mammalian and plant pathogenic bacteria. This type of secretion system has been associated with the trans-location of proteins from bacteria into target cells of the host. We have previously shown that the hrp/hrmA gene cluster isolated from Pseudomonas syringae Pss61 encodes for the conserved components of a putative type III protein export apparatus (PEA) as well as an apparently dedicated regulatory system involving HrpL. Pathogenesis by P. syringae is thus likely to involve adhesion of the bacteria to plant cells, plant cell contact-dependent induction of hrp gene expression, assembly of a hrp-encoded type III PEA and translocation of virulence and host range determinants into target plant cells. The mechanisms for coordinating assembly of the PEA have only been partially characterized thus far. The overall goal of this project will be to elucidate the mechanisms controlling assembly of the hrp-encoded PEA and define the role of the PEA in the pathogenicity of P. syringae strains. In the proposed experiments we will: 1) complete the characterization of the HrpL-dependent regulatory system; 2) use a novel reporter gene system to dissect the secretion pathway for Avr products; and 3) employ a genetic screen to identify the genetic determinants regulated by HrpL-linked regulatory system. Plants have the capability to recognize and respond to invading pathogens to protect themselves and thereby minimize disease. This involves recognition of pathogen signals by the cells of the plant. The hrp genes of Pseudomonas syringae have been shown to function in the recognition process and the products of these bacterial genes are predicted to form an apparatus that injects proteins into plants cells. These injected proteins are the stimulus to which the plant cells respond. These experiments will use a genetic approach to investigate early steps in the recognition process. Elucidation of the regulation a nd function of the hrp-encoded secretion apparatus will influence current research in molecular plant-microbe interactions by providing insights into: 1) molecules and regulatory pathways controlling disease resistance in plants; 2 innate mechanisms controlling pathogenicity of bacteria in plants; 3) new strategies for breeding stable crop resistance against a broad array of pathogens by targeting specific attributes of the pathogen; and 4) evolution of protein secretion systems functioning in the pathogenicity of mammalian and plant pathogens.