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

根瘤菌是关键的共生体，它们感染豌豆植物及其近亲（豆科植物）的根，为它们的宿主固定氮以换取碳。然而，全球变化正在改变碳和氮的营养流动，而碳和氮是根瘤菌与其宿主之间贸易的货币。在一些土壤中，由于化石燃料燃烧造成的污染，氮含量增加了100多倍。进化理论预测，在这种极端环境下，控制共生关系的宿主系统会退化，可能会释放出剥削性共生体的流行病。本项目研究了豆科植物及其共生体在氮污染下的快速进化。遗传和表型分析将解决加州不同氮污染水平人群之间的差异，并将揭示根瘤菌利用的程度和分子机制。该项目将加深我们对根瘤菌共生的认识，根瘤菌共生对野生植物至关重要，并通过促进作物生长和生物燃料生产为生物经济提供重要服务。该项目还将(i)培训中学生并直接让他们参与数据收集，（ii）开发一门以科学方法及其在社会和政策相关决策中的应用为重点的大学课程，以及（iii）启动一项微生物研究培训计划，目标是来自科学领域代表性不足的群体的本科生。

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.