Host Control of Intracellular Bacteria Survival in the Nitrogen-fixing Symbiosis

对于植物的生长，氮素的有效性往往是限制因素。虽然大多数作物依赖氮肥，其中大部分是化学合成的，但豆类具有非凡的能力，通过与固氮菌进入共生关系来提供自己的氮素营养，将空气中原本惰性的氮气转化为氨。由于合成化学氮肥消耗大量化石燃料，化肥径流导致环境退化，充分利用固氮共生的潜力可以为可持续的未来做出贡献。这个项目的目的是在分子水平上了解豆类作物如何具有其他作物所没有的能力，使固氮菌参与生产性共生。它将确定关键植物基因的功能，这些基因是细菌与宿主协同工作所必需的。发现固氮共生的机理将对社会产生广泛的有益影响，并将在多个层面上向具有科学素养的公众传播。植物和动物与微生物伙伴进行复杂而复杂的相互作用，其中一些对宿主有害，另一些对宿主有利。在豆科植物与固氮根瘤菌的共生过程中，单个细菌被寄主摄取并转化为膜结合的固氮细胞器。该领域的最新进展表明，这个细胞内隔间是由来自宿主的一个特殊的蛋白质分泌系统维持的，该系统提供关键蛋白质来调节宿主-微生物界面。这项研究的核心是了解宿主分泌蛋白与微生物相互作用的机制，以确保细菌在共生的细胞内阶段的生存。这些发现将极大地促进我们对宿主和他们的微生物伙伴之间的分子对话的理解。

For the growth of plants the availability of nitrogen is frequently the limiting factor. While most crops rely on nitrogen fertilizer, much of it chemically synthesized, legumes have the remarkable ability to provide their own nitrogen nutrition by entering a symbiotic relationship with nitrogen-fixing bacteria, converting otherwise inert nitrogen gas in the air into ammonia. Because synthesizing chemical nitrogen fertilizers consumes massive amounts of fossil fuel and fertilizer runoff causes environmental degradation, harnessing the full potential of nitrogen-fixing symbiosis can contribute to a sustainable future. This project aims to understand at the molecular level how legumes have the capacity, absent in other crops, to engage nitrogen-fixing bacteria in a productive symbiosis. It will identify the function of key plant genes necessary to allow the bacteria to work in concert with the host. Discovering the mechanism of the nitrogen-fixing symbiosis will have broad beneficial impacts on the society, which will be communicated at multiple levels to a scientifically literate public. Plants and animals engage in complex and elaborate interactions with microbial partners, some detrimental and others beneficial to the host. During the symbiosis between legume and nitrogen-fixing rhizobia, individual bacteria are ingested by the host and converted to membrane-bound nitrogen-fixing organelles. Recent advances in the field showed that this intracellular compartment is sustained by a specialized protein secretory system from the host, which delivers key proteins to modulate the host- microbe interface. This research project centers on understanding the mechanisms by which host secretory proteins interact with the microbe to ensure the survival of the bacteria during the intracellular stage of the symbiosis. The findings will significantly advance our understanding of the molecular dialog between hosts and their microbial partners.