Studies On The Molecular Systematics Of Physaraceae And Trichiales

The taxonomic position of myxomycetes in organisms is still controversy due to the life cycle which contains distinctly some features of both protist and fungus. Meanwhile, the consisting members of myxomycetes have varied widely. Aimed to establish a authentic taxonomic system, the small subunit rDNA from some species of Trichiales and Physaraceae have been amplified by PCR and sequenced in this paper. The systematic relationships between these groups have been obtained by comparing and analyzing the sequences. The results will be helpful to establish a natural taxonomic system.The small subunit ribosomal DNA from Diachea bulbillosa was firstly amplified by PCR method and sequenced. The result indicated that Diachea were more closely related to Physarales than to Stemonitales, and supported that it would be more reasonable to place Diachea in Phyarales more than in Stemonitales.The small subunit rDNA from 5 species, 4 genera of Physaraceae were amplified by PCR method and sequenced. The molecular phylogenetic analyses of these sequences support to divide these species of Physaraceae into two clades, Physarum, Leocarpus, Diachea and Craterium formed a clade, and Physwerella and Fuligo formed another clade. On the phylogenetic relationships among the 6 genera, Fuligo and Physwerella formed the basal position among Physaraceae, and the other four genera diverged in the folloing order Leocarpus, Diachea Craterium and Physarum.The small subunit rDNA from 4 species, 4 genera of Trichiales were amplified by PCR method and sequenced. The results of the sequence analyses support that Metatrichia and Trichia were the most closely related to each other on relationship, and they were more closely related to Hemitrichia than Arcyria. Meanwhile , On the phylogenetic relationships of the 4 genera, Hemitrichi is diverged relative early, Arcyria and Trichia were relative later, Metatrichia was between the two groups. The molecular systematics results suggested that Arcyriaceae and Trichiaceae should not be combined together, and it was necessary to divide Trichiales into three families.The molecular systematics results obtained in this study may provid important molecular biological evidences for the studies on the origin and evolution of slime molds. But further researches were needed for some groups were excluded,.