title: Basidioascus undulatus: genome, origins, and sexuality.
abstract: Basidioascus undulatus is a soil basidiomycete belonging to the order Geminibasidiales. The taxonomic status of the order was unclear as originally it was only tentatively classified in the class Wallemiomycetes. The fungi in Geminibasidiales have an ambiguously defined sexual cycle. In this study, we sequenced the genome of B. undulatus to gain insights into its sexuality and evolutionary origins. The assembled genome draft was approximately 32 Mb in size, had a median nucleotide coverage of 24X, and contained 6123 predicted genes. Previous morphological descriptions of B. undulatus relied on interpretation of putative sexual structures. In this study, nuclear staining and confocal microscopy showed meiosis occurring in basidia and genome analysis confirmed the existence of genes involved in meiosis and mating. Using 35 protein-coding genes extracted from genomic information, phylogenomic and molecular dating analyses confirmed that B. undulatus indeed belongs to a lineage distantly related to Wallemia while retaining a basal position in Agaricomycotina. These results, combined with differences in septal pore morphology, led us to move the order Geminibasidiales out of the Wallemiomycetes and into the new class Geminibasidiomycetes cl. nov. Finally, the concept of Agaricomycotina is emended to include both Wallemiomycetes and Geminibasidiomycetes.
authors.affiliation: Department of Biology, Faculty of Science, University of Ottawa, 30 Marie Curie, Ottawa, Ontario, K1N 6N5, Canada; ; Biodiversity (Mycology), Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, 960 Carling Ave., Ottawa, Ontario, K1A 0C6, Canada.
authors.forename: Hai D T
authors.initials: HD
authors.lastname: Nguyen
authors.affiliation: Microscopy Centre, Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, 960 Carling Ave., Ottawa, Ontario, K1A 0C6, Canada.
authors.forename: Denise
authors.initials: D
authors.lastname: Chabot
authors.affiliation: Department of Biology, Faculty of Science, University of Ottawa, 30 Marie Curie, Ottawa, Ontario, K1N 6N5, Canada; ; Biodiversity (Mycology), Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, 960 Carling Ave., Ottawa, Ontario, K1A 0C6, Canada.
authors.forename: Yuuri
authors.initials: Y
authors.lastname: Hirooka
authors.affiliation: School of Life Sciences, Arizona State University, Tempe, AZ 85287-1601, USA.
authors.forename: Robert W
authors.initials: RW
authors.lastname: Roberson
authors.affiliation: Department of Biology, Faculty of Science, University of Ottawa, 30 Marie Curie, Ottawa, Ontario, K1N 6N5, Canada; ; Biodiversity (Mycology), Eastern Cereal and Oilseed Research Centre, Agriculture and Agri-Food Canada, 960 Carling Ave., Ottawa, Ontario, K1A 0C6, Canada.
authors.forename: Keith A
authors.initials: KA
authors.lastname: Seifert
keywords: Agaricomycotina; Basidiomycota; Geminibasidiomycetes; Wallemiomycetes; septal pore ultastructure