Ureide metabolism and abiotic stress in plants

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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.