Yu Liu

University of Toronto, Toronto, Ontario, Canada

Are you Yu Liu?

Claim your profile

Publications (3)26.4 Total impact

  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Resolving the evolutionary relationships among Fungi remains challenging because of their highly variable evolutionary rates, and lack of a close phylogenetic outgroup. Nucleariida, an enigmatic group of amoeboids, have been proposed to emerge close to the fungal-metazoan divergence and might fulfill this role. Yet, published phylogenies with up to five genes are without compelling statistical support, and genome-level data should be used to resolve this question with confidence. Our analyses with nuclear (118 proteins) and mitochondrial (13 proteins) data now robustly associate Nucleariida and Fungi as neighbors, an assemblage that we term 'Holomycota'. With Nucleariida as an outgroup, we revisit unresolved deep fungal relationships. Our phylogenomic analysis provides significant support for the paraphyly of the traditional taxon Zygomycota, and contradicts a recent proposal to include Mortierella in a phylum Mucoromycotina. We further question the introduction of separate phyla for Glomeromycota and Blastocladiomycota, whose phylogenetic positions relative to other phyla remain unresolved even with genome-level datasets. Our results motivate broad sampling of additional genome sequences from these phyla.
    BMC Evolutionary Biology 11/2009; 9:272. · 3.29 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Several morphologically dissimilar ascomycete fungi including Schizosaccharomyces, Taphrina, Saitoella, Pneumocystis, and Neolecta have been grouped into the taxon Taphrinomycotina (Archiascomycota or Archiascomycotina), originally based on rRNA phylogeny. These analyses lack statistically significant support for the monophyly of this grouping, and although confirmed by more recent multigene analyses, this topology is contradicted by mitochondrial phylogenies. To resolve this inconsistency, we have assembled phylogenomic mitochondrial and nuclear data sets from four distantly related taphrinomycotina taxa: Schizosaccharomyces pombe, Pneumocystis carinii, Saitoella complicata, and Taphrina deformans. Our phylogenomic analyses based on nuclear data (113 proteins) conclusively support the monophyly of Taphrinomycotina, diverging as a sister group to Saccharomycotina + Pezizomycotina. However, despite the improved taxon sampling, Taphrinomycotina continue to be paraphyletic with the mitochondrial data set (13 proteins): Schizosaccharomyces species associate with budding yeasts (Saccharomycotina) and the other Taphrinomycotina group as a sister group to Saccharomycotina + Pezizomycotina. Yet, as Schizosaccharomyces and Saccharomycotina species are fast evolving, the mitochondrial phylogeny may be influenced by a long-branch attraction (LBA) artifact. After removal of fast-evolving sequence positions from the mitochondrial data set, we recover the monophyly of Taphrinomycotina. Our combined results suggest that Taphrinomycotina is a legitimate taxon, that this group of species diverges as a sister group to Saccharomycotina + Pezizomycotina, and that phylogenetic positioning of yeasts and fission yeasts with mitochondrial data is plagued by a strong LBA artifact.
    Molecular Biology and Evolution 11/2008; 26(1):27-34. · 14.31 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: To generate data for comparative analyses of zygomycete mitochondrial gene expression, we sequenced mtDNAs of three distantly related zygomycetes, Rhizopus oryzae, Mortierella verticillata and Smittium culisetae. They all contain the standard fungal mitochondrial gene set, plus rnpB, the gene encoding the RNA subunit of the mitochondrial RNase P (mtP-RNA) and rps3, encoding ribosomal protein S3 (the latter lacking in R.oryzae). The mtP-RNAs of R.oryzae and of additional zygomycete relatives have the most eubacteria-like RNA structures among fungi. Precise mapping of the 5' and 3' termini of the R.oryzae and M.verticillata mtP-RNAs confirms their expression and processing at the exact sites predicted by secondary structure modeling. The 3' RNA processing of zygomycete mitochondrial mRNAs, SSU-rRNA and mtP-RNA occurs at the C-rich sequence motifs similar to those identified in fission yeast and basidiomycete mtDNAs. The C-rich motifs are included in the mature transcripts, and are likely generated by exonucleolytic trimming of RNA 3' termini. Zygomycete mtDNAs feature a variety of insertion elements: (i) mtDNAs of R.oryzae and M.verticillata were subject to invasions by double hairpin elements; (ii) genes of all three species contain numerous mobile group I introns, including one that is closest to an intron that invaded angiosperm mtDNAs; and (iii) at least one additional case of a mobile element, characterized by a homing endonuclease insertion between partially duplicated genes [Paquin,B., Laforest,M.J., Forget,L., Roewer,I., Wang,Z., Longcore,J. and Lang,B.F. (1997) Curr. Genet., 31, 380-395]. The combined mtDNA-encoded proteins contain insufficient phylogenetic signal to demonstrate monophyly of zygomycetes.
    Nucleic Acids Research 02/2005; 33(2):734-44. · 8.81 Impact Factor

Publication Stats

117 Citations
26.40 Total Impact Points

Institutions

  • 2009
    • University of Toronto
      Toronto, Ontario, Canada
  • 2008–2009
    • Université du Québec à Montréal
      • Department of Chemistry
      Montréal, Quebec, Canada
    • Dalhousie University
      Halifax, Nova Scotia, Canada
  • 2005
    • Canadian Institute For Advanced Research
      Toronto, Ontario, Canada