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

对于植物的生长来说，氮的有效性常常是限制因素。虽然大多数作物依赖氮肥，其中大部分是化学合成的，但豆类通过与固氮细菌的共生关系，将空气中惰性的氮气转化为氨，从而具有提供自身氮营养的非凡能力。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，因此充分利用固氮共生的潜力可以为可持续的未来做出贡献。该项目旨在从分子水平上了解豆科植物如何具有其他作物所缺乏的能力，使固氮细菌参与到生产共生中。它将确定关键植物基因的功能，这些基因是使细菌与宿主协同工作所必需的。发现固氮共生机制将对社会产生广泛的有益影响，这将在多个层面上传达给具有科学素养的公众。植物和动物与微生物伴侣进行复杂而精细的相互作用，有些对宿主有害，有些对宿主有益。在豆科植物与固氮根瘤菌的共生过程中，单个细菌被寄主吸收并转化为膜结合的固氮细胞器。该领域的最新进展表明，这种细胞内隔室是由宿主专门的蛋白质分泌系统维持的，该系统提供调节宿主-微生物界面的关键蛋白质。本研究项目的重点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存活。这些发现将极大地促进我们对宿主及其微生物伙伴之间分子对话的理解。

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.