Regulation of ureide metabolism in legumes

豆科植物固氮是全球氮循环的重要自然机制。豆科植物可以与土壤细菌形成共生关系，形成称为根瘤的特殊根结构。植物将通过光合作用获得的碳提供给细菌，细菌将大气中的氮（蛋白质、DNA和其他生物分子的基本成分）转化为植物可以利用的形式。这个过程被称为固氮。在农业豆科植物中，这为人类和牲畜的饮食提供了一个重要的氮供应机制，并且需要更少的人工氮肥。在大豆和相关豆科植物中，固定氮以尿素的形式从根瘤转移到叶子、豆荚和种子中，然后在那里被分解，使氮得到利用。当水变得有限时，尿素积累，固氮停止。这个过程对水的限制非常敏感，但我们还不知道为什么。研究计划的总体主题将是豆科植物氮代谢的分子和生化调控。重点将是尿素代谢和固氮。具体目标包括鉴定与尿毒素代谢有关的基因，并确定如何调节尿毒素分解代谢。该研究项目将整合植物生理学、生物化学和分子生物学，以增强我们对豆科植物中尿素代谢的理解。目前，对尿素代谢的调控尚不清楚，这一过程尚未在任何豆科作物物种的分子水平上进行研究。随着氮肥价格因能源成本上升而上涨，豆类生产变得更有吸引力，因为它既是具有生物燃料潜力的作物，也是需要较少人工氮肥的作物。了解控制氮素分解代谢和固氮的调节机制，以应对非生物胁迫，特别是气候变化可能带来的胁迫，对于通过管理实践、育种或生物技术提高豆科植物的产量至关重要。

Nitrogen fixation in legumes is an important natural mechanism in the global nitrogen cycle. Legumes can form symbioses with soil bacteria to develop specialized root structures called nodules.   The plant supplies carbon, obtained through photosynthesis, to the bacteria and the bacteria convert atmospheric nitrogen, a  fundamental component of protein, DNA and other biomolecules, to a form usable by the plant.  This process is called nitrogen fixation.  In agricultural legumes, this provides an important mechanism to supply nitrogen to the diets of humans and livestock and requires far less artificial nitrogen fertilization.In soybean and related legumes, fixed nitrogen moves as ureides from the nodules to leaves, pods and seeds, where they are then broken down, allowing the nitrogen to be utilized.  When water becomes limiting, ureides build up and nitrogen fixation ceases.  This process is extremely sensitive to water limitation, but we do not yet understand why.  The overall theme of the research program will be molecular and biochemical regulation of nitrogen metabolism in legumes.  The focus will be ureide metabolism and nitrogen fixation. Specific objectives include the identification of genes involved in ureide metabolism and determining how ureide catabolism is regulated.  The research program will integrate plant physiology, biochemistry and molecular biology to augment our understanding of ureide metabolism in legume species.  Currently, regulation of ureide metabolism is poorly characterized and this process has not been examined in any legume crop species at the molecular level.  As nitrogen fertilizer prices increase in response to rising energy costs, legume production becomes more attractive, both as crops with potential for biofuels, as well as those requiring less artificial nitrogen fertilizer.  Understanding the regulatory mechanisms controlling ureide catabolism and nitrogen fixation in response to abiotic stresses, particularly those that may be brought on by climate change, will be critical in improving legume production through management practices, breeding or biotechnology.