Biological Role of Motility in the Plant Pathogenic Bacterium Ralstonia Solanacearum

植物病原菌青枯菌运动性的生物学作用

• 批准号: 0090692
• 负责人: Caitilyn Allen
• 金额: $ 35万
• 依托单位: University of Wisconsin-Madison
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2001
• 资助国家: 美国
• 起止时间: 2001-02-15 至 2004-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0090692&HistoricalAwards=false
• 关键词: Biological; Role; Motility; Plant; Pathogenic

Most plant-associated bacteria can move, even though motility uses much energy and may elicit host defense responses. The ability to move is known to help bacteria pathogenic to animals, but the role of bacterial motility in plant pathogenesis is largely unexplored. Two well-characterized nonmotile mutants of the plant pathogen, Ralstonia solanacearum, caused significantly less disease on tomato in a realistic soil invasion virulence assay, showing that this trait does contribute to virulence. The goal of this project is to combine genetic, histopathological, and ecological approaches to comprehensively describe the role of motility in the life history of this plant-associated bacterium. The first objective is to determine how motility contributes to organismal fitness. The investigators will microscopically examine tomato roots infected with fluorescent motile or nonmotile bacteria to compare the behavior of these strains during the early stages of pathogenesis. These experiments will test the hypothesis that motility plays a key role early in host invasion and colonization. To test the hypothesis that motility late in disease development is actively disadvantageous, the investigators will measure the virulence of a regulatory mutant that is always motile. Because motility is likely to affect bacterial fitness outside the plant as well, they will compare soil survival of motile and nonmotile strains to test the hypothesis that motility increases saprophytic survival in soil and decaying plant material. The second objective is to separate the effects of bacterial movement from those of the flagella themselves, because flagella may mediate attachment to plant surfaces and recognition by the host. To determine if flagella attach bacteria to plant surfaces, investigators will compare attachment of non-flagellated and flagellated but paralyzed mutants to tomato roots. Analysis of plant biochemical responses and defense gene expression will reveal whether host plants recognize purified R. solanacearum flagella or their component flagellins. The third objective is to explore how R. solanacearum regulates its motility. This trait is likely controlled by a complex hierarchy involving an internally responsive flagellar regulon, known virulence factor regulators, and host plant signals. Investigators will use reporter gene fusions and regulatory mutants to define motility gene regulation in this species. Because R. solanacearum motility in culture does not reflect the behavior of the pathogen in its natural habitat, gene expression studies will be conducted in planta. Collectively, the experiments proposed here will yield an integrated understanding of how the ability to move helps, and possibly hinders, this bacterium throughout its complex life cycle.

大多数与植物相关的细菌可以移动，即使运动消耗大量能量并可能引起宿主防御反应。 已知移动能力有助于细菌对动物致病，但细菌运动性在植物致病中的作用在很大程度上未被探索。 两个良好的特点nonmotile突变体的植物病原体，青枯雷尔氏菌，引起番茄在一个现实的土壤入侵毒力测定显着减少疾病，表明这一特性有助于毒力。 该项目的目标是结合联合收割机遗传学，组织病理学和生态学的方法，全面描述运动的作用，这种植物相关的细菌的生活史。 第一个目标是确定运动性如何有助于生物体适应性。 研究人员将用显微镜检查感染荧光运动或非运动细菌的番茄根，以比较这些菌株在发病早期阶段的行为。 这些实验将检验运动在宿主入侵和定殖早期起关键作用的假设。 为了检验疾病发展后期的运动性是积极不利的这一假设，研究人员将测量总是运动的调节突变体的毒力。 由于运动性也可能影响植物外部的细菌适应性，他们将比较运动和非运动菌株的土壤存活率，以检验运动性增加土壤和腐烂植物材料中的腐殖化存活率的假设。 第二个目标是将细菌运动的影响与鞭毛本身的影响分开，因为鞭毛可以介导植物表面的附着和宿主的识别。 为了确定鞭毛是否将细菌附着在植物表面，研究人员将比较无鞭毛和有鞭毛但瘫痪的突变体与番茄根部的附着。 分析植物的生化反应和防御基因的表达将揭示寄主植物是否识别纯化的R。青枯菌鞭毛或其组分鞭毛蛋白。 第三个目标是探索R.青枯菌调节其运动性。 这种性状可能是由一个复杂的层次结构，涉及内部响应鞭毛调节子，已知的毒力因子调节器，和宿主植物信号控制。 研究人员将使用报告基因融合和调节突变体来定义该物种的运动基因调节。 因为R.培养物中的青枯菌运动性不能反映病原体在其自然栖息地中的行为，因此将在植物中进行基因表达研究。 总的来说，这里提出的实验将产生一个综合的理解，如何移动的能力帮助，并可能阻碍，这种细菌在其复杂的生命周期。