MSB: Bacterial endosymbionts of arbuscular mycorrhizal fungi: ecology and evolution

Cornell University, Ithaca NY

Investigators

Abstract

The goal of this project is to understand the interaction between arbuscular mycorrhizal (AM) fungi (phylum Glomeromycota) and bacteria that reside in their hyphae and spores. AM fungi and their endobacteria are components of a tri-partite symbiotic association that also includes the majority of terrestrial plants, and may be one of the most common symbioses on the planet. AM fungi colonize roots of land plants and assist in the uptake of mineral nutrients to the plant in exchange for plant-assimilated carbon. Endobacteria of AM fungi associated with dune vegetation of the North Atlantic coast of the U. S. were selected as a focal system for the study. A survey of endobacteria distribution among AM fungal lineages combined with reconstruction of phylogenies of the interacting partners will enable inferences about the evolutionary origin, the age of the association, and the phylogentic relationships of endobacteria with their free-living relatives. A reconstruction of the population structure of endobacteria will clarify their reproductive and transmission mode. An assessment of the effects that harboring endobacteria has on the fungal and plant fitness will reveal whether endobacteria are parasites or mutualists of AM fungi. This study will enhance understanding of the biology of AM fungi and of the functioning of arbuscular mycorrhizae in terrestrial ecosystems, including agroecosystems. It will provide insights into the interactions of bacteria with fungi in general, and expand the knowledge of evolutionary processes involved in the establishment and maintenance of endosymbiotic interactions. By focusing on AM fungi that occur naturally in coastal dunes, this project will contribute to the efforts to conserve and restore the fragile dune habitat. A graduate student and several undergraduate and high school students will be trained in the course of the project.