Molecular Characterization of the Pseudomonas Syringae hrp hrm Gene Cluster.

了解植物中细菌致病性的分子基础的关键是植物防御激发子和宿主范围决定因子的产生和部署。我们之前已经证实从丁香假单胞菌pv中分离到hrp/hrm基因簇。丁香61使非致病性细菌引发植物防御。因此，hrp/hrm基因簇似乎构成了足以产生植物防御启动子的最小遗传单位。14个明显的跨国单位已被确定在集群组织为9个明显的转录单位。几个hrp基因作为正调控元件。本项目的总体目标是阐明特定hrp/hrm基因在确定丁香假单胞菌致病性和宿主范围中的作用。我们的方法将是：1)获得集群剩余部分的核苷酸序列，以便于以后的操作，与其他细菌的比较分析和基因功能的推断；2)表征HRP基因表达的调控级联，从而识别和操纵直接参与植物防御启动子产生的基因；3)进行基因替代实验，检测HRP特异性基因在决定致病性和宿主范围中的作用。对这些基因的研究应该会导致有用的技术来阻止对易受细菌感染的植物的损害。

A key to understanding the molecular basis for bacterial pathogenicity in plants is the production and deployment of plant defense elicitors and host range determinants. We have previously shown that the hrp/hrm gene cluster isolated from Pseudomonas syringae pv. syringae 61 enables nonpathogenic bacteria to elicit plant defenses. The hrp/hrm gene cluster, therefore, appears to constitute a minimum genetic unit sufficient to produce plant defense elicitors. Fourteen apparent transnational units have been identified within the cluster that are organized as nine apparent transcriptional units. Several hrp genes act as positive regulatory elements. The overall goal of this project is to elucidate the role of specific hrp/hrm genes in determining the pathogenicity and host range of P. syringae strains. Our approach will be to: 1) obtain the nucleotide sequence for remaining portions of the cluster to facilitate later manipulation, comparative analyses with other bacteria and deduction of gene function; 2) characterize the regulatory cascade controlling expression of hrp genes so that the genes directly contributing to the production of plant defense elicitors can be identified and manipulated; and 3) perform gene replacement experiments to test the role of specific hrp genes in determining pathogenicity and host range. %%% The study of these genes should lead to techniques useful in stopping the damage to plants susceptible to bacterial infection.