Ureide metabolism and abiotic stress in plants

生物固氮是全球氮循环的组成部分。豆科植物与土壤细菌形成共生关系，形成称为根瘤的特殊根结构。植物向细菌提供光合作用产生的碳，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。在农业豆科植物中，这是向人类和牲畜提供氮的重要机制，同时限制氮肥的施用。在大豆和相关豆科植物中，固定氮以氮化物的形式从根瘤转移到叶片、豆荚和种子中，然后被分解，氮被利用。当水变得有限时，尿素积累，固氮停止。这个过程对水分限制极其敏感，我们已经表明，尿素也会在活性氧（ROS）的响应下积累，可能是一种一般的非生物应激反应。我的长期研究方向是氮代谢的分子与生化调控，重点研究尿素代谢与非生物胁迫。具体目标包括检测缺乏尿素代谢的突变体对非生物应激的敏感性，确定这些基因在响应ROS和其他应激源时的表达时间和地点，并解决它们对固氮的影响。我的研究项目将继续整合植物生理学、生物化学和分子生物学，以增强我们对尿素代谢的理解。在植物的分子水平上，对尿素代谢的调控仍知之甚少。随着氮肥价格因能源成本上升而上涨，增加豆类产量变得更具吸引力。随着粮食安全问题日益严重，豆类也提供了一种广泛获取的植物性膳食蛋白质来源。了解在应对非生物胁迫，特别是气候变化可能带来的胁迫时控制尿素代谢和固氮的调节机制，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。

Biological nitrogen fixation is integral to the global nitrogen cycle. Legumes form symbioses with soil bacteria resulting in specialized root structures called nodules. The plant supplies carbon, derived from 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. In agricultural legumes, this is an important mechanism to supply nitrogen to the diets of humans and livestock while limiting nitrogen fertilization. In soybean and related legumes fixed nitrogen moves from the nodules to leaves, pods and seeds as ureides, which are then broken down and the nitrogen utilized. When water becomes limiting, ureides build up and nitrogen fixation ceases. This process is extremely sensitive to water limitation, and we have shown that ureides also accumulate in response to reactive oxygen species (ROS), likely a general abiotic stress response. The long term theme of my research program is molecular and biochemical regulation of nitrogen metabolism, with a focus on ureide metabolism and abiotic stress. Specific objectives include testing mutants deficient in ureide metabolism for sensitivity to abiotic stress, identifying when and where these genes are expressed in response to ROS and other stressors and addressing their impact on nitrogen fixation. My research program continues to integrate plant physiology, biochemistry and molecular biology to augment our understanding of ureide metabolism.Regulation of ureide metabolism is still poorly characterized at the molecular level in plants. As nitrogen fertilizer prices increase in response to rising energy costs, increased legume production becomes more attractive. With increased food security concerns legumes also offer a broadly accessible plant-based source of dietary protein. Understanding the regulatory mechanisms controlling ureide metabolism 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.