Molecular phylogeny of Trametes and related genera based on internal transcribed spacer (ITS) and nearly complete mitochondrial small subunit ribosomal DNA (mt SSU rDNA) sequences

摘要

Some species of?Trametes?and their related genera are so similar in microstructure characteristics that it is difficult to identify and separate them by traditional taxonomy. In this study, we elucidated relationships among?Trametes?through comparison of the nuclear internal transcribed spacer (ITS) and the nearly complete mitochondrial small subunit ribosomal DNA (mt SSU rDNA) sequences. Finally, phylogenetic trees were built. Phylogenetic analysis of the ITS and mt SSU rDNA sequences showed consensus results; most of the?Trametes?species clustered within a single clade and formed a main clade together with species of?Pycnoporus. The genera?Coriolopsisand?Cerrena?could be separated clearly from the main clade. The determination of secondary structure of the ITS1 and ITS2 domains of the representative species indicated that the conservative structure of some helices might be useful for resolving the phylogenetic relationship among some related species. The secondary structures of the variable domains V4 and V6 in mt SSU rDNA were also determined in this study. We found that both the conserved domains and the variable domains all contained informative sites which could significantly contribute to resolving the phylogenetic relationships within the?Trametes?group. The length and sequences of the V4 and V6 domains were found to be constant within a species, but very different among species with significant inter-species variations. The major advantage of these species-specific markers is that we only need to study one isolate from one species to determine their phylogenetic position. Secondary structure information of the V4 and V6 domains is found to be a useful marker to resolve phylogenetic problems. Based on our study, we considered that the genus?Pycnoporus?had a close relationship with?Trametes;?Trametes trogii?was grouped with?Coriolopsis gallica, indicating that it might belong to?Coriolopsis;?Cerrena, as a separate genus, was placed far away from?Trametes.