Study On Molecular Systematics Of Trametes And Relative Genera

Trametes and their relative genera are important groups of Polyporaceae. They are widely separated in the nature and some species of Trametes have been widely used in medical and environmental space. At the present time, the taxonomy of Trametes is primarily based on morphological features, just like the spore features, the hyphal types and the rotting habit etc. Unfortunately, some species of Trametes and their related genera are so similar in microstructure characteristics that it's difficult to identify and separate them by traditional taxonomy. Sometimes the taxonomy based on morphological characteristics is not reliable and it is liable to cause confusion and controversy. With the development of molecular systematics, many nucleotide sequences provide the most direct evidences for evolution and classification study. So these sequences have been widely used in molecular systematics research of some fungi. In this study, the internal transcribed spacer (ITS) and the nearly complete sequences of mitochondrial small-subunit ribosomal DNA (mt SSU rDNA) were cloned and sequenced. Phylogeny of Trametes and the relative gerena were studied based on the two sequences and other relative sequences from GenBank database, finally the phylogenetic trees were built respectively and the secondary structure of some area was constructed. The main results were summarized as follows:(1) Phylogenetic analysis of the ITS and mt SSU rDNA sequences showed consensus results that most of the Trametes species clustered within a single clade and formed the main clade together with the species of Pycnoporus. The secondary structure of Trametes and Pycnoporus was also similar with each other. All these results proved that Pycnoporus have very close relationship with Trametes.(2) Our study showed that Trametes elegans belong to Trametes, it grouped with Trametes species and had close relationship with Pycnoporus.(3) The genus of Coriolopsis could be separated clearly from the Trametes clade in both of the ITS tree and the mt SSU rDNA tree, Coriolopsis trogii, which had confuse phylogenetic position in former studies, was grouped with Coriolopsis, and the secondary structure of Coriolopsis trogii was also different with Trametes. Basing on these, we considered that Coriolopsis trogii belongs to Coriolopsis.(4) Cerrena unicolor was far away from Trametes, it could be separated clearly from the Trametes in phylogenetic trees and the secondary structure of it was quit different from Trametes. According to these, we considered that it was not fitting to use Cerrena unicolor as the representative species of the Trametes group. (5) The determination of secondary structure of the ITS1 and ITS2 domains had the consensus results with the phylogenetic trees. Some base changes in the ITS sequences might not affect the stability of the secondary structure. With that feature, the secondary structure of ITS region could be used in resolving some phylogenetic relationship problems which the sequences were so variable that it had some difficult in sequences alignment. And it also showed that the conservative structure of some helices might be useful for resolving the phylogenetic relationship among some related species.(6) We found that both the conserved domains and the variable domains all contained informative sites which could significantly contribute in resolving phylogenetic relationships among Trametes group. Secondary structure information of the variable domains is found to be a useful marker to resolve the phylogenetic problems. The length and sequences of the V4 and V6 domains were found to be constant within a species, but quiet different between two 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, and that might reduce lots of work in phylogenetic reaserch.