EAGER: Mycoplasma-related Endobacteria of Arbuscular Mycorrhizal Fungi: Life History and Evolutionary Genomics

Cornell University, Ithaca NY

Investigators

Abstract

This project will investigate the biology of MRE and transform understanding of ecosystem functioning in similar ways as the recognition of the role of AM fungi in plant ecology transformed the understanding of plant community dynamics. Furthermore, if MRE are indeed parasites of Glomeromycota, then understanding how their ancient asexual fungal hosts dealt with parasite pressure will become a pressing issue of general interest. Finally, identifying forces that drive MRE population dynamics will be important for understanding genome evolution in MRE and their Mycoplasma relatives. The project includes opportunities for graduate, undergraduate, and high school students, including research experiences in microbiology, molecular genetics, and bioinformatics. Undergraduates will be recruited through the Microbial Friends & Foes REU and the Cornell Office of Undergraduate Biology, and high school students through BOCES. More than half of the students mentored by the PI have been from groups underrepresented in science. The PI works with the Cornell Office of Academic Diversity Initiatives to create training opportunities for minority undergraduates. The goal of this project is to understand the life history and evolutionary genomics of the newly discovered mycoplasma-related endobacteria (MRE) of arbuscular mycorrhizal (AM) fungi (phylum Glomeromycota). AM fungi and their endobacteria are components of a complex symbiotic association that also includes the majority of terrestrial plants, and may be one of the most common multi-partner symbioses on the planet. AM fungi colonize roots of land plants and assist in the uptake of mineral nutrients in exchange for plant-assimilated carbon. Thus, AM fungi are pivotal in shaping the structure and function of terrestrial ecosystems. While the biology of MRE is largely unknown, they are distributed in all major lineages of Glomeromycota and exhibit substantial genetic variability within individuals of their AM fungal hosts. This pattern is inconsistent with evolutionary theory in that mutualistic endosymbionts are predicted to be genetically uniform within a host. Consequently, it is hypothesized that MRE are parasites and that their genomes exhibit features consistent with a parasitic lifestyle. This project will integrate the ecology and evolutionary genomics of MRE to elucidate their role in the Glomeromycota. (1) An assessment of the effects of MRE infection on host fitness will reveal whether MRE are parasites or mutualists. (2) Sequencing and de novo assembly of MRE genomes will enable inferences about MRE metabolic features. (3) Elucidating forces that drive MRE population dynamics will reveal mechanisms responsible for MRE genome evolution.