The Single Origin of Mycorrhizas Among the Amanita: A Model for Elucidating the Genetic Architecture of Symbiosis

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Mycorrhizas are ubiquitous symbioses between plants and root-associated fungi; in exchange for carbon, the fungi provide plants with either phosphorus or nitrogen. Interactions among different species of plants and fungi control local patterns of biodiversity, and species ranges are often shaped by the availability of local partners. The fungal genus Amanita is an emerging model for exploring how organisms associated in obligate symbioses are distributed and established in a changing world. Amanita is a common, widely-distributed and diverse genus encompassing both mycorrhizal and decomposer species and provides a rare opportunity to compare the genetic architecture of closely related symbiotic and free-living fungi. The central questions of proposed research include: (1) what genes or gene families define symbiosis? (2), after the evolution of symbiosis, what happens to genes normally required for independent growth? Methods involve comparative analyses of genetic data taken from different Amanita species grown either in symbiosis with a live plant, or with dead plant materials. Data will elucidate whether or not symbiotic species maintain the capacity for independent growth, and how this affects species ranges in response to global change. Shifts may subsequently influence the biogeography of associated plant species. The results will be directly relevant to the nascent biofuels industry; the decomposition of plant materials is a rate-limiting step in biofuels production, and the identification of genes directly responsible for decomposition will inform the development of more effective degradative enzymes. Outreach includes the development of new, permanent exhibits about symbiosis at the Harvard Museum of Natural History. The HMNH is visited by more than 179,000 persons annually, including approximately 25,000 schoolchildren and their teachers, and serves as Boston?s major natural history museum. Developed media will also be widely distributed for use by other museums and in classrooms.