POWRE: Biological Role of Motility in Bacterial Wilt of Plants

许多细菌能够移动，使用被称为鞭毛的螺旋桨状结构。尽管向宿主移动或在宿主内移动的能力赋予了某些动物病原体显著的选择性优势，但细菌在植物相关微生物中的运动作用尚不清楚。青枯病是一种可移动的植物病原菌，可引起多种植物的青枯病。当青枯菌在实验室培养时，其细胞只有在低细胞密度下才能活动，这可能与该细菌在寄主植物入侵和定殖的早期阶段在自然界中遇到的条件相对应。PI将通过创造一个不能移动的青枯病菌突变体来检验这一假设，即运动性有助于细菌植物病原体的成功。这种无性突变体的侵袭性将结合实际的土壤毒力分析、定时根浸渍分析和对标记突变体和野生型菌株的显微分析来量化。该物种仅在寄主植物入侵和定殖早期阶段活动的假设将直接通过检测植物木质部导管生长过程中的细菌运动性来检验，并间接通过测量植物木质部导管生长过程中运动性基因的表达来检验。这将决定青枯病菌基因在培养物中的表达是否反映了病原菌在其宿主中的行为。测量两个调节突变背景中的运动性基因表达将确定细菌运动性如何适应青枯病菌复杂的基因表达网络。这项研究将阐明一个世界性的、灵活的模型病原体生命周期中的一个关键阶段。这项建议在以下方面符合POWRE计划的指导方针：a)它为P.I.打开了一条全新的研究调查路线；b)P.I.在妇女和科学领域负有重大的行政责任(她是植物病理学和妇女研究系的联合任命，也是校园妇女在科学和工程计划中的系主任)；以及，c)P.I.在家庭假中断后最近恢复了她的职业生涯。

Many bacteria are able to move, using propeller-like structures called flagella. Although the ability to move towards or within a host confers a significant selective advantage on some animal pathogens, the role of bacterial motility in plant-associated microbes is not known. One motile plant pathogen, Ralstonia solanacearum, causes bacterial wilt disease of many diverse plant species. When R. solanacearum grows in laboratory culture, its cells are motile only at low cell densities, possibly corresponding to conditions the bacterium encounters in nature during the early stages of host plant invasion and colonization. The PI will test the hypothesis that motility contributes to the success of bacterial plant pathogens by creating a nonmotile mutant of R. solanacearum. Invasiveness of this nomnotile mutant will be quantified using a combination of realistic soil virulence assays, timed root dip assays, and microscopic analysis with marked mutant and wildtype strains. The hypothesis that this species is motile only during host plant invasion and early stages of colonization will be tested directly by assaying bacterial motility during growth in the plant xylem vessel and indirectly by measuring expression of motility genes during growth in the plant xylem vessel. This will determine whether R. solanacearum gene expression in culture reflects the behavior of the pathogen in its host. Measuring motility gene expression in two regulatory mutant backgrounds will determine how bacterial motility fits into R. solanacearum's complex gene expression network. This research will elucidate a critical stage in the life cycle of a cosmopolitan and flexible model pathogen.This proposal fits the POWRE Program guidelines in the following ways: a) it opens an entirely new line of research inquiry for the P.I.; b) the P.I. has substantial administrative responsibilities in the area of women and science (she is jointly appointed in the Plant Pathology and Women's Studies departments, and also serves as Faculty Director of the campus Women in Science and Engineering Program); and, c) the P.I. recently resumed her career after an interruption for family leave.