Cellular Responses to Quaternary Ammonium Compounds by Pseudomonas Syringae that Influence its Interactions with Plants

丁香假单胞菌对季铵化合物的细胞反应影响其与植物的相互作用

• 批准号: 0920156
• 负责人: Gwyn Beattie
• 金额: $ 58.17万
• 依托单位: Iowa State University
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2009
• 资助国家: 美国
• 起止时间: 2009-08-15 至 2013-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0920156&HistoricalAwards=false
• 关键词: Cellular; Responses; Quaternary; Ammonium; Compounds

Intellectual Merit Plants are colonized by a diversity of microorganisms, including many that influence plant and environmental health. Plants produce a class of compounds called quaternary ammonium compounds (QACs) that are important to plant membranes and to plant tolerance to drought and salinity stress. These compounds, including betaine, carnitine, and choline, may also benefit plant-associated bacteria. For example, betaine can confer protection to stresses, choline can serve as a building block for some bacterial membrane lipids, and choline-O-sulfate may help store sulfur. Most plant-associated bacteria, including the plant pathogen Pseudomonas syringae, cannot synthesize QACs and thus are dependent on production by the host. Consequently, these organisms have likely evolved mechanisms to import and exploit these compounds. In support of this, the ability to transport choline was recently shown to provide a clear fitness benefit to P. syringae during its colonization of plants. Moreover, studies characterizing the full set of P. syringae transporters for choline and betaine uptake identified additional novel cellular components that may be involved in QAC metabolism and regulation. The goals of this project are to characterize the responses of P. syringae to specific plant-derived QACs and evaluate how these responses influence P. syringae interactions with plants. To address these goals, first, carnitine will be examined as an attractant and nutrient source by investigating the role of a newly identified carnitine-responsive chemotaxis protein in directing bacterial movement to germinating seedlings, and by identifying the genes required for carnitine catabolism and their contribution to fitness. Second, choline-O-sulfate will be evaluated as a source of sulfur and nutrients by characterizing how the loss of transport and catabolism impact P. syringae fitness on plants and by more extensively characterizing the cellular components involved in choline-O-sulfate uptake. And third, betaine, choline, phosphorylcholine and phosphatidylcholine will be evaluated as signal molecules for bacteria by examining global gene expression patterns in P. syringae mutants that lack the ability to degrade individual compounds and thus are able to accumulate them. These studies will significantly advance our understanding of how the perception, signaling and metabolism of this special class of compounds by P. syringae influences the ability of this widely studied bacterial pathogen to colonize plants. Plant-associated P. syringae populations are relevant not only as reservoirs of pathogens for plant disease, but also as reservoirs of biological ice nuclei that may have a role in atmospheric processes leading to rain. Insights into the impact of QACs on leaf-associated bacterial populations are of timely importance because increases in drought, as predicted by global climate change models, and salinity, as is occurring in large areas of irrigated agricultural lands, can result in increased QAC abundance in plant tissues, due to either natural accumulation or agricultural engineering to improve drought and salinity tolerance. Broader Impacts This project will contribute to education by providing training for one graduate student and significant research experiences for at least five undergraduate students, several of which are expected to be members of under-represented groups in the sciences. Outreach activities will provide internships for two biology teachers (7th-12th grade) through an established program at Iowa State University for biology teachers, with the subsequent co-development and implementation of discovery-based curricula based on bacterial ice nucleation and leaf colonization. Outreach activities will also include directing at least two workshops to advance the involvement of middle school students from under-represented groups in the sciences through the Science Bound program at Iowa State University, and co-directing a workshop on plant pathogens for elementary students and their parents.

有智慧的植物被各种各样的微生物侵占，包括许多影响植物和环境健康的微生物。植物产生一类被称为季铵化合物(QAC)的化合物，这种化合物对植物细胞膜和植物对干旱和盐分胁迫的耐受性非常重要。这些化合物，包括甜菜碱、肉碱和胆碱，也可能有利于植物相关细菌。例如，甜菜碱可以为压力提供保护，胆碱可以作为某些细菌膜脂的积木，O-硫代胆碱可能有助于储存硫。大多数植物相关细菌，包括植物病原菌丁香假单胞菌，不能合成QAC，因此依赖于宿主的生产。因此，这些生物很可能进化出了进口和利用这些化合物的机制。为了支持这一点，运输胆碱的能力最近被证明在紫丁香根结线虫在植物上定居期间对其提供了明显的健康益处。此外，对全套丁香根结线虫胆碱和甜菜碱吸收转运体的研究确定了可能参与QAC代谢和调节的其他新的细胞成分。本项目的目标是描述丁香疫霉对特定植物来源的QAC的反应，并评估这些反应如何影响丁香疫霉与植物的相互作用。为了达到这些目标，首先，将通过研究新发现的肉碱反应趋化蛋白在引导细菌运动到萌发幼苗中的作用，以及通过鉴定肉碱分解代谢所需的基因及其对适应能力的贡献，来研究肉碱作为引诱剂和营养源的作用。其次，将通过表征运输和分解代谢的丧失如何影响紫丁香对植物的适合性，以及通过更广泛地表征参与胆碱-O-硫酸盐吸收的细胞成分，来评估O-胆碱-硫酸盐作为硫磺和营养物质的来源。第三，甜菜碱、胆碱、磷胆碱和磷脂酰胆碱将被评估为细菌的信号分子，方法是研究紫丁香突变体的全球基因表达模式，这些突变体缺乏降解单个化合物的能力，从而能够积累它们。这些研究将极大地促进我们对紫丁香菌对这类特殊化合物的感知、信号和代谢如何影响这种被广泛研究的细菌病原体在植物上定殖的能力。与植物相关的紫丁香种群不仅是植物病害病原体的储存库，也是可能在导致降雨的大气过程中起作用的生物冰核的储存库。深入了解QAC对叶片相关细菌种群的影响具有及时的重要性，因为全球气候变化模型预测的干旱增加和大片灌溉农田发生的盐分增加可能导致植物组织中QAC丰度的增加，这是由于自然积累或农业工程提高干旱和盐分耐受性。该项目将通过为一名研究生提供培训，并为至少五名本科生提供重要的研究经验，从而为教育做出贡献，其中几名本科生预计将成为科学界代表性不足群体的成员。外展活动将通过在爱荷华州立大学为生物教师制定的计划，为两名生物教师(7-12年级)提供实习机会，随后共同开发和实施基于发现的课程，以细菌冰核和树叶定植为基础。外展活动还将包括指导至少两个研讨会，通过爱荷华州立大学的科学方向项目，促进来自代表性不足群体的中学生参与科学，并共同指导为小学生及其家长举办的植物病原体研讨会。