Almost 90% of legumes are able to form nitrogen-fixing root nodules in symbiosis with soil rhizobia. Nodulated, nitrogen-fixing legumes produce bioavailable nitrogen, which is one characteristic that make legumes second only to the cereals in their importance to human nutrition. Symbiotic nitrogen fixing root nodule development is a complex process requiring coordination of both the plant host and rhizobial symbionts' differentiation pathways. In previous collaborative work between the Dickstein and Sherrier laboratories, two Medicago truncatula plant mutants, nip (numerous infections with polyphenolics) and sli (sluggish infections) defective in the rhizobial infection/invasion process were identified and partially characterized. The current work seeks to define the molecular and cellular defect underpinning these mutations. The intellectual merits of this project include: (1) cell biological analyses of mutants to facilitate the map-based cloning of the nip, and (2) characterization of sli with cell biological approaches. The broader impacts of the project include examination of important aspects of the basic biology of nodule development, IT growth and symbiosome formation, which have previously been difficult to study. The results of this research might lead to new strategies to improve the efficiency of nodulation and nitrogen fixation. Other broader impacts include the training of a postdoctoral fellow, graduate students, and undergraduate students. Additionally, both Drs. Dickstein and Sherrier's groups are involved in several outreach programs at their respective universities that recruit non-mainstream undergraduate students, underrepresented minority undergraduate students, high school teachers in the summer, and high school students to their respective laboratories.
