A multi-gene phylogeny for Stachybotrys evidences lack of trichodiene synthase (tri5) gene for isolates of one of three intrageneric lineages.
Members of the mitosporic fungal form-genus Stachybotrys, including common indoor contaminants Stachybotrys chartarum, Stachybotrys echinata and Stachybotrys chlorohalonata, are capable of producing potent, protein synthesis-inhibiting, trichothecene mycotoxins. A combined multi-gene approach was used to investigate relationships among species of Stachybotrys against which the presence/absence of the trichothecene biosynthetic pathway gene, trichodiene synthase (tri5), was evaluated. Phylogenetic analyses partitioned species of Stachybotrys into three strongly supported lineages, two of which contained common indoor taxa. No tri5 PCR product was amplified from members of the third clade, which included the only member of the group with a known sexual state, Stachybotrys albipes. Isolates grouped with S. albipes also tested negative for tri5 in Southern analyses. The phylogenetic distribution of tri5 was consistent with known toxin production for the group. For isolates with tri5 product, Bayesian analysis suggested that signal from amino acid determining sites conflicted with the combined phylogeny. Incongruence however, was not supported by either SH-test results or maximum likelihood analyses. Moreover, sites rates analysis showed that tri5 was highly conserved at the amino acid level suggesting that identity at variable sites, among otherwise divergent taxa, might be the result of chance events.
Department of Ecology and Evolutionary Biology, University of Toronto, 25 Willcocks Street, Toronto, Ontario, Canada. brenda.koster@gmail.com
Brenda
B
Koster
Bess
B
Wong
Neil
N
Straus
David
D
Malloch
D019755:Carbon-Carbon Lyases / Q000235:genetics* / Q000378:metabolism; D004783:Environmental Microbiology; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D008969:Molecular Sequence Data; D010802:Phylogeny; D013191:Stachybotrys / Q000145:classification* / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D014255:Trichothecenes / Q000096:biosynthesis
D005656:Fungal Proteins; D014255:Trichothecenes; D019755:Carbon-Carbon Lyases; C051130:trichodiene synthetase