Relationships of microsporidian genera, with emphasis on the polysporous genera, revealed by sequences of the largest subunit of RNA polymerase II (RPB1)

Molecular data have proved useful as an alternative to morphological data i n showing the relationships of genera within the phylum Microsporidia, but until now have been available only for ribosomal genes. In previous studies protein-coding genes of microsporidia have been used only to assess their position in the evolution of eukaryotes. For the first time we report on th e use of a protein-coding gene, the A-G region of the largest subunit of RN A polymerase II (RPB1) from 14 mainly polysporous species, to generate an a lternative phylogeny for microsporidia. Using the amino acid sequences, the genera and species fell into the same main groupings as had been obtained with 16S rDNA sequences, bur the RPB1 data provided better resolution withi n these groups. The results supported the pairings of Trachipleistophora ho minis with Vavraia culicis and Pleistophora hippoglossoideos with Pleistoph ora typicalis. They also confirmed that the genus Pleistophora is not monop hyletic and that it will be necessary to transfer Pleistophora ovariae and Pleistophora mirandellae into one or more other genera, as has already been effected for Pleistophora anguillarum.