Collaborative Research: Chemotactic signaling in Sinorhizobium meliloti symbiotic plant host interaction

趋化性使活动细菌能够远离有害的化学物质，向有益的化学物质移动。根瘤菌是一种独特的可移动土壤细菌，它可以与豆科植物如豌豆、大豆和苜蓿进行特定的共生关系。这种共生关系为寄主植物提供氮，这是植物生长最具限制性的营养物质。趋化过程使根瘤菌能够识别并向寄主移动，从而改善共生关系，从而促进植物生长。根瘤菌利用多种化学受体蛋白来感知宿主植物分泌的多种化合物。然而，关于敏感性和适应性调节的具体过程知之甚少，这是有效趋化反应的基本特征。这个项目的首要目标是解码控制刺激适应的途径。结果将改变我们目前对细菌趋化性及其与真核宿主相互作用的生物学概念。这项研究的结果可能会减少人工肥料的使用，从而直接有利于未来的农业和环境问题，从而降低农业的成本和污染。更广泛的影响活动包括研究的内在优点，因为固氮是生物圈中最重要的过程之一。此外，该项目将涉及研究生的跨学科培训。该团队致力于指导研究生和本科生，特别是代表性不足的人群和女性。公共推广活动包括让小学生和中学生在校内和校外动手演示，以及让本科生和高中生参与研究。模式植物共生Sinorhizobium meliloti的趋化系统比肠道细菌进化得更复杂。虽然最近发现了一些控制趋化性的独特成分和特征，但通路敏感性和刺激适应性的调节尚不清楚。本课题旨在阐明在这一过程中起关键作用的受体修饰系统。具体来说，一种新的趋化蛋白，CheT的功能，它前所未有地与适应途径的保守元件相互作用，将被破译。首先，研究人员将描述控制适应性的趋化途径。在寄主植物感知中起核心作用的两种化学受体，即氨基酸传感器McpU和甜菜碱传感器McpX，将被作为模型，因为它们有望与适应途径表现出不同的相互作用模式。行为、微观和突变分析以及质谱分析将用于揭示刺激适应的分子基础。其次，将通过遗传、行为、磷酸化和结构分析来阐明CheT在趋化信号传导中的作用。提出的研究将推进复杂感觉系统的知识。该奖项反映了美国国家科学基金会的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Chemotaxis enables motile bacteria to move away from harmful and towards beneficial chemicals. One unique group of motile soil bacteria are rhizobia, which can engage in specific symbiotic relationships with leguminous plants such as peas, soy beans, and alfalfa. This symbiosis supplies the host plant with nitrogen, which is the most limiting nutrient for plant growth. The process of chemotaxis allows rhizobia to recognize and move towards its host, which improves the symbiotic relationship, and consequently, enhances plant growth. Multiple chemoreceptor proteins are being used by rhizobia to sense a wide spectrum of chemical compounds secreted by the host plants. However, little is known about the specific processes involved in the regulation of sensitivity and adaptation, which are essential features for an effective chemotactic response. The overarching goal of this project is to decode the pathway that controls stimuli adaptation. Outcomes will transform our current concepts of the biology of bacterial chemotaxis and their interaction with their eukaryotic hosts. The results of this research can directly benefit future agricultural and environmental issues by potentially reducing the use of artificial fertilizers, resulting in less expensive and less polluting agriculture. Broader Impacts activities include the intrinsic merit of the research as nitrogen fixation is one of the most important processes in the biosphere. In addition, the project will involve the interdisciplinary training of graduate students. The team is committed to mentoring graduate and undergraduate students, especially underrepresented populations and women. Public outreach activities include hands-on demonstrations for elementary and high school students, both on- and off-campus, and involvement of undergraduate and high school students in research.The chemotaxis system of the model plant symbiont Sinorhizobium meliloti evolved a greater complexity than that of enteric bacteria. Although several unique components and features controlling chemotaxis have been recently uncovered, regulation of pathway sensitivity and stimuli adaptation are unknown. The aim of this research project is to elucidate the receptor modification system, which plays a pivotal role in this process. Specifically, the function of a novel chemotaxis protein, CheT, which unprecedentedly interacts with a conserved element of the adaptation pathway, will be deciphered. First, the investigators will characterize the chemotactic pathway controlling adaptation. Two chemoreceptors with a central role in host-plant sensing, namely amino acid sensor McpU and betaine sensors McpX, will serve as models because they are expected to exhibit different modes of interaction with the adaptation pathway. Behavioral, microscopic, and mutational analyses, as well as mass spectrometry will be used to uncover the molecular basis for stimuli adaptation. Second, the role of CheT in chemotactic signaling will be elucidated through genetic, behavioral, phosphorylation, and structural analyses. The proposed research will advance knowledge of complex sensory systems.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.