Submitted to: Federation Of European Microbiological Societies Yeast Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: September 7, 2012
Publication Date: January 15, 2013
Citation: Kurtzman, C.P., Robnett, C.J. 2013. Relationships among genera of the Saccharomycotina (Ascomycota) from multigene phylogenetic analysis of type species. Federation Of European Microbiological Societies Yeast Research. 13(1):23-33. Interpretive Summary: This study presents an analysis of genetic relationships among ascomycetous yeasts. The nearly 70 genera included in this study separate into eleven major groups (clades), all of which have arisen from a common ancestor. This study provides a clarification of relationships among the yeasts that is important to several areas of science. Classification can now be based on natural relationships, and because unique biochemical pathways are often shared by members of genetically related groups, the classification system can be used to predict the occurrence of biotechnologically important metabolic pathways. For example, fermentation of wood sugar to fuel alcohol is a property shared by two major species groups, and metabolism of methanol, a biotechnologically important pathway, is also shared by two major groups. The information provided in this study will be used by taxonomists, biotechnologists, agricultural scientists, clinicians, and others needing to rapidly identify yeasts from gene sequences.
Technical Abstract: Phylogenetic relatedness among ascomycetous yeast genera (subphylum Saccharomycotina, phylum Ascomycota) has been uncertain. In the present study, type species of 70 currently recognized genera are compared from divergence in the nearly entire nuclear gene sequences for large subunit rRNA, small subunit rRNA, translation elongation factor-1a, and RNA polymerase II, subunits 1 (RPB1) and 2 (RPB2). The analysis substantiates earlier proposals that all known ascomycetous yeast genera now assigned to the Saccharomycotina represent a single clade. Maximum likelihood analysis resolved the taxa into eight large multi-genus clades and three single genus clades. Genera of the family Saccharomycetaceae remain as one large clade as previously demonstrated to which the genus Cyniclomyces is now assigned. Pichia, Saturnispora, Kregervanrija, Dekkera, Ogataea, and Ambrosiozyma are members of a single large clade, which is separate from the clade that includes Barnettozyma, Cyberlindnera, Phaffomyces, Starmera, and Wickerhamomyces. Other clades include Kodamaea, Metschnikowia, Debaryomyces, Cephaloascus, and related genera, which are separate from the clade that includes Zygoascus, Trichomonascus, Yarrowia, and others. This study once again demonstrates that there is limited congruence between a classification system based on phenotype and a phylogeny determined from gene sequences. The five genes used in this analysis have provided a moderately robust tree, but resolution of some nodes must await an analysis based on a much larger number of genes, such as available from whole genome sequencing.