RoL: Regulation of cell envelope homeostasis in the alpha-proteobacterium Sinorhizobium meliloti

生物适应、生存，甚至茁壮成长。有些生物通过与另一种完全不同的生物相互作用而更成功地发挥作用，这两种生物一起做一些它们各自都不能做的事情。这可能对两种生物都有利，使其成为互惠共生。生物体是如何合作的，而不是一个生物体引起另一个生物体的疾病？我们的项目在植物及其细菌共生体的情况下解决了这些问题。由于细菌提供了可用的氮，这种伙伴关系对环境和农业的可持续性至关重要。我们的工作将采用几种方法来发现植物寄主如何适应并与其细菌伴侣交流。除了这种特殊的共生关系，我们的工作推动了理解微生物-宿主相互作用的一般规则的前沿。共生现象在生物世界中有多普遍？微生物群落如何与宿主相互作用，成本和收益是什么？我们在这个项目中开发的实验方法，以及我们在研究中取得的发现，将推动共生的一般领域，也将有助于微生物组和疾病的研究。该项目支持STEM社区，并将通过纳入关于固氮共生的新高中科学课程来增加其多样性。这些课堂和实验室模块将把植物科学与生态学和营养学结合起来，并提供在可持续农业中使用豆类的历史和跨文化背景。新课程将特别吸引拉丁裔和美洲原住民血统的学生。根瘤菌-豆科植物的共生经历了一系列的阶段，在植物宿主和细菌伴侣之间进行着不断的识别和交流。虽然共生的早期阶段已经得到了很好的研究，并且已经分析了信号分子和分子反应，但对晚期感染和早期分化的阶段知之甚少。包括我们在内的几个研究小组之前的工作已经确定了短形紫花苜蓿dnf突变体（固氮缺陷），这些突变体在meliloti Sinorhizobium类细菌成熟中存在缺陷。一种植物突变体dnf1是加工结节型富含半胱氨酸（NCR）肽所必需的，而其他dnf突变体本身编码NCR肽。通过转录和突变分析，我们确定了一组细菌基因，即“L2簇”，它似乎在类细菌分化之前被下调。l2簇基因集富含被预测在细胞包膜稳态中起作用的基因。我们同时发现，细胞包膜应激反应与寄主植物感染所需的细胞外多糖的调节有关。结合遗传学、分子生物学和细胞生物学的方法，我们将剖析细胞包膜应激反应的机制，并确定其与共生的关系。我们将通过利用植物突变分析以及细菌感染和分化的体内细胞和分子报告分析来进一步探索植物寄主如何控制细菌L2簇。共同资助项目：生活规则；植物生物相互作用；细胞动力学与功能。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。

Organisms adapt, survive and even thrive. Some function more successfully by interacting with another completely different kind of organism, where the two do something together that neither can do on its own. This may benefit both organisms, making it a mutualistic symbiosis. How do organisms manage to cooperate instead of one causing disease in the other? Our project addresses such questions in the case of a plant and its bacterial symbiont. With the bacteria providing usable nitrogen, this partnership is fundamental to environmental and agricultural sustainability. Our work will employ several approaches to discover how the plant host accommodates and communicates with its bacterial partner. Beyond this particular symbiosis, our work pushes back the frontier of understanding the general rules for microbe-host interactions. How prevalent are symbioses in the living world? How do communities of microbes interact with hosts, and what are the costs and benefits? The experimental approaches we develop in this project, and the discoveries we make in our research, will advance the general field of symbiosis and will also contribute to microbiome and disease research. The project supports the STEM community and will increase its diversity by incorporating new high school science curricula on nitrogen-fixing symbiosis. These classroom and laboratory modules will tie together plant science with ecology and nutrition and provide historical and cross-cultural context on the use of legumes in sustainable agriculture. The new curricula will be of particular interest to students of Latinx and native American ancestry. Rhizobia-legume symbioses proceed through a series of stages with ongoing recognition and communication between the plant host and bacterial partner. While early stages of symbiosis have been well studied, and signal molecules and molecular responses have been analyzed, less is known about the stages of late infection and early differentiation. Previous work from several research groups including ours have identified Medicago truncatula dnf mutants (defective in nitrogen fixation) that are defective in Sinorhizobium meliloti bacteroid maturation. One plant mutant, dnf1, is required for processing of nodule cysteine-rich (NCR) peptides, and other dnf mutants encode NCR peptides themselves. By transcription and mutant analyses, we identified a set of bacterial genes, the "L2 cluster", which appear to be downregulated just prior to bacteroid differentiation. The L2-cluster gene set is enriched for genes predicted to function in cell envelope homeostasis. We concurrently discovered that cell envelope stress responses are tied to regulation of extracellular polysaccharides, which are required for host plant infection. With a combination of genetic, molecular, and cell biology approaches, we will dissect the mechanism for cell envelope stress response and define its relationship to symbiosis. We will further explore how the plant host controls the bacterial L2 cluster by exploiting plant mutation analysis together with in vivo cell and molecular reporter analysis of bacterial infection and differentiation. Co-funding Programs: Rules of Life; Plant Biotic Interactions; Cellular Dynamics and Function.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.