When nitrogen is limited in soils most legume plants form nitrogen-fixing nodules on their roots in symbiosis with soil bacteria called rhizobia. Nodulated legumes utilize bioavailable nitrogen produced within the nodule, reducing nitrogen fertilizer requirements, thereby lowering energy costs and environmental pollution associated with crop production. Recently a gene called NIP was found to be essential for the development of symbiotic nodules in the model legume plant Medicago truncatula. This project seeks to determine the role of NIP in nodule formation and root differentiation. Experiments will discern NIP's developmental and temporal patterns of gene expression in nodules and roots and test how NIP expression at artificially high levels affects nodulation. Cellular approaches will determine where the NIP gene and encoded protein are expressed. The biochemical function of the NIP protein, a predicted transporter, will be assessed in a foreign host as well as directly in wild-type plants and those with a genetic defect in the NIP gene. Physiological experiments will discern whether the NIP transporter is acting as part of a sensor system. The results from these experiments will yield information on the biochemical function of the NIP protein and provide a context for understanding NIP function in nodulation and other plant development pathways. The broader impacts of this project include adding to the knowledge base of nodule development, part of what makes legume plants valuable in agriculture as a source of high-protein, high-fiber food for humans and animals. Training opportunities for a post-doctoral fellow, graduate and undergraduate students in the areas of molecular and cell biology, genetics and biochemistry will be provided by this project.
