CAREER: EVOLUTION OF HOST CONTROL OVER SYMBIOSIS, DYSBIOSIS IN ANTHROPOGENIC LANDSCAPES

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Rhizobial bacteria are key symbionts that infect the roots of pea plants and their relatives (legumes) and fix nitrogen for their hosts in exchange for carbon. Yet global changes are now altering nutrient fluxes of carbon and nitrogen that are the currency of trade between rhizobia and their hosts. In some soils, nitrogen levels have increased more than 100-fold due to pollution from fossil fuel combustion. Evolutionary theory predicts degradation of host systems that control symbiosis in such extreme settings, potentially unleashing epidemics of exploitative symbionts. This project investigates the rapid evolution of legumes and their symbionts in response to nitrogen pollution. Genetic and phenotypic analyses will resolve differences among populations in California that vary in nitrogen pollution levels and will uncover the extent and molecular mechanisms of rhizobial exploitation. This project will enhance our understanding of rhizobial symbioses, which are critical to wild plants and provide an important service to the bio-economy via enhanced crop growth and biofuel production. This project will also (i) train middle-school students and directly involve them in gathering data, (ii) develop a college course focused on the scientific method and its application to social and policy-related decisions, and (iii) initiate a microbiology-research training program that targets undergraduate students from groups underrepresented in the sciences.