title: Molecular evolution patterns reveal life history features of mycoplasma-related endobacteria associated with arbuscular mycorrhizal fungi.
abstract: The mycoplasma-related endobacteria (MRE), representing a recently discovered lineage of Mollicutes, are widely distributed across arbuscular mycorrhizal fungi (AMF, Glomeromycota). AMF colonize roots of most terrestrial plants and improve plant mineral nutrient uptake in return for plant-assimilated carbon. The role of MRE in the biology of their fungal hosts is unknown. To start characterizing this association, we assessed partitioning of MRE genetic diversity within AMF individuals and across the AMF phylogeographic range. We further used molecular evolution patterns to make inferences about MRE codivergence with AMF, their lifestyle and antiquity of the Glomeromycota-MRE association. While we did not detect differentiation between MRE derived from different continents, high levels of diversity were apparent in MRE populations within AMF host individuals. MRE exhibited significant codiversification with AMF over ecological time and the absence of codivergence over evolutionary time. Moreover, genetic recombination was evident in MRE. These patterns indicate that, while MRE transmission is predominantly vertical, their complex intrahost populations are likely generated by horizontal transmission and recombination. Based on predictions of evolutionary theory, we interpreted these observations as a suggestion that MRE may be antagonists of AMF. Finally, we detected a marginally significant signature of codivergence of MRE with Glomeromycota and the Endogone lineage of Mucoromycotina, implying that the symbiosis between MRE and fungi may predate the divergence between these two groups of fungi.
authors.affiliation: School of Integrative Plant Science, Plant Pathology & Plant Microbe-Biology, Cornell University, Ithaca, NY, 14853, USA.
authors.forename: Kevin H
authors.initials: KH
authors.lastname: Toomer
authors.affiliation: School of Integrative Plant Science, Plant Pathology & Plant Microbe-Biology, Cornell University, Ithaca, NY, 14853, USA.|State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan, 430070, China.
authors.forename: Xiuhua
authors.initials: X
authors.lastname: Chen
authors.affiliation: School of Integrative Plant Science, Plant Pathology & Plant Microbe-Biology, Cornell University, Ithaca, NY, 14853, USA.
authors.forename: Mizue
authors.initials: M
authors.lastname: Naito
authors.affiliation: School of Integrative Plant Science, Plant Pathology & Plant Microbe-Biology, Cornell University, Ithaca, NY, 14853, USA.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Mondo
authors.affiliation: School of Integrative Plant Science, Plant Pathology & Plant Microbe-Biology, Cornell University, Ithaca, NY, 14853, USA.
authors.forename: Henk C
authors.initials: HC
authors.lastname: den Bakker
authors.affiliation: School of Integrative Plant Science, Plant Pathology & Plant Microbe-Biology, Cornell University, Ithaca, NY, 14853, USA.
authors.forename: Nicholas W
authors.initials: NW
authors.lastname: VanKuren
authors.affiliation: MPG Ranch, Missoula, MT, 59802, USA.|Department of Ecosystem and Conservation Sciences, University of Montana, Missoula, MT, 59812, USA.
authors.forename: Ylva
authors.initials: Y
authors.lastname: Lekberg
authors.affiliation: Division of Plant & Soil Sciences, West Virginia University, Morgantown, WV, 26506, USA.
authors.forename: Joseph B
authors.initials: JB
authors.lastname: Morton
authors.affiliation: School of Integrative Plant Science, Plant Pathology & Plant Microbe-Biology, Cornell University, Ithaca, NY, 14853, USA.
authors.forename: Teresa E
authors.initials: TE
authors.lastname: Pawlowska
mesh_terms: D019143:Evolution, Molecular; D014644:Genetic Variation; D055137:Glomeromycota; D006239:Haplotypes; D008969:Molecular Sequence Data; D009174:Mycoplasma / Q000235:genetics*; D038821:Mycorrhizae; D010802:Phylogeny; D058974:Phylogeography; D018517:Plant Roots / Q000382:microbiology; D017422:Sequence Analysis, DNA; D013559:Symbiosis
keywords: Claroideoglomus etunicatum; Gigasporaceae; Glomeromycota; horizontal transmission; parasitism; vertical transmission