Monophyly of lampreys and hagfishes supported by nuclear DNA-coded genes

The phylogenetic position of hagfishes in vertebrate evolution is currently controversial. The 18S and 28S rRNA trees support the monophyly of hagfish es and lampreys. In contrast, the mitochondrial DNAs suggest the close asso ciation of lampreys and gnathostomes. To clarify this controversial issue, we have conducted cloning and sequencing of the four nuclear DNA-coded sing le-copy genes encoding the triose phosphate isomerase, calreticulin, and th e largest subunit of RNA polymerase II and III. Based on these proteins, to gether with the Mn superoxide dismutase for which hagfish and lamprey seque nces are available in database, phylogenetic trees have been inferred by th e maximum likelihood (ML) method of protein phylogeny. It was shown that al l the five proteins prefer the monophyletic tree of cyclostomes, and the to tal log-likelihood of the five proteins significantly supports the cyclosto me monophyly at the level of +/-1 SE. The ML trees of aldolase family com p rising three nonallelic isoforms and the complement component group compris ing C3, C4, and C5, both of which diverged during vertebrate evolution by g ene duplications, also suggest the cyclostome monophyly.