Molecular Analysis of Avirulence and Basic Pathogenicity Genes in Xanthomonas Campestris pv Vesicatoria

油菜黄单胞菌无毒分离株的培养能力。辣椒对近等基因抗性品种或广泛分化品种的过敏反应是由特定的毒力基因控制的。在这一提案中，我们计划描述种族特异性无毒基因avrBs1和avrBs2，以及独特的非宿主无毒基因avrZ的成员。这些基因的分子特征将提供一个坚实的分子基础，这将使我们能够比较蛋白质产物的结构相似性或差异以及无毒基因表达的调节。这些基因的特征和各自蛋白的多克隆抗血清的生产将使我们能够设计实验来阐明细胞识别和随后的信号转导过程中涉及的生化过程，这些过程负责引发植物防御机制。Hrp基因簇的互补分析及其与特定无毒基因的可能功能关系将通过定义该DNA区域的遗传组织和特定突变对无毒基因表达调控的影响来解决。最后，本研究将探讨小镰刀虱对非寄主物种的寄主范围排斥的分子遗传控制，并确定决定抗性的植物寄主基因的遗传模式。许多植物病原体遵循一种“基因对基因”的关系，即它们是否会在特定的寄主植物品系中引起疾病。只有当病原体携带其自身某一基因的特定等位基因，而宿主携带其自身某一基因的特定等位基因时，疾病才会发生。这些特定病原体和宿主基因的其他等位基因的任何组合都可以排除疾病。这种遗传关系已经被理解了40年，但是决定疾病发生的基因的生化功能仍然完全不清楚。斯塔斯卡维茨博士是第一批成功从植物病原体中分离出疾病决定基因的研究人员之一。在这个项目中，他将对这些基因的产物进行表征，以便为了解宿主-病原体相互作用的分子基础奠定基础。除了其内在的生物学意义外，这项工作对未来的植物病害控制也具有明显的实际意义。

The ability of avirulent isolate of Xanthomonas campestris pv. vesicatoria to induce a hypersensitive reaction on near- isogenic resistant cultivars of Capsicum annuum or widely divergent species is controlled by the presence of specific avirulence genes. In this proposal, we plan to characterize the race-specific avirulence genes, avrBs1 and avrBs2, and a member of unique class of non-host avirulence genes, avrZ. The molecular characterization of these genes will provide a solid molecular foundation which will allow us to compare structural similarities or differences in protein products and regulation of avirulence gene expression. The characterization of these genes and the production of polyclonal antisera to their respective proteins will put us into a position to design experiments to elucidate the biochemical processes involved in cellular recognition and the subsequent signal transduction processes responsible for eliciting plant defence mechanisms. The complementation analysis of the Hrp gene cluster and its possible functional relationship with specific avirulence genes will addressed by defining the genetic organization of this region of DNA and the effects of specific mutations on the regulation of avirulence gene expression. Finally, we will investigate the molecular genetic control of host range exclusion in X. c. vesicatoria on non-host species and determine the inheritance patterns of plant host genes that determine resistance. Many plant pathogens follow a "gene-for-gene" relationship with regard to whether or not they cause disease in a particular strain of host plant. Disease ensues only when the pathogen carries a specific allele of one of its own genes, and when the host carries a specific allele of one of its own genes. Any combination of other alleles of these particular pathogen and host genes precludes disease. This genetic relationship has been understood for forty years, but the biochemical functions of the genes involved in the determination of the occurrence of disease have remained completely obscure. Dr. Staskawicz has been one of the first investigators to succeed in isolating disease- determining genes from a plant pathogen. In this project he will characterize the products of these genes, in order to lay the foundation for understanding of the molecular basis of the host-pathogen interaction. Apart from its intrinsic biological interest, this work also has obvious practical importance for future efforts to control plant diseases.