Molecular evolution of ependymin and the phylogenetic resolution of early divergences among euteleost fishes.

摘要: The rate and pattern of DNA evolution ependymin, a single-copy gene coding for highly expressed glycoprotein in the brain matrix teleost fishes, is characterized its phylogenetic utility fish systematics assessed. sequences were determined from catfish, electric fish, characiforms compared with published ependymin cyprinids, salmon, pike, herring. Among these groups, amino acid divergent (up to 60% sequence difference), but had surprisingly similar hydropathy profiles invariant glycosylation sites, suggesting that functional properties proteins are conserved. Comparison base composition at third codon positions introns revealed AT-rich GC-rich positions, biased usage observed might not be due mutational bias. Phylogenetic information content was high sufficient recover most basal nodes tree, spite observation pairwise distances (at positions) well above presumed saturation level. This finding can explained by proportion phylogenetically informative nonsynonymous changes among proteins. Ependymin have established first molecular evidence monophyly group containing salmonids esociforms. In addition, suggests sister relationship (Gymnotiformes) Characiformes, constituting significant departure currently accepted classifications. However, relationships characiform lineages completely resolved seemingly appropriate levels variation taxa considerably low homoplasy data (consistency index = 0.7). If diversification Characiformes took place an "explosive" manner, over relatively short period time this should also using other markers. Poor conservation ependymin's primary structure hinders design efficient primers PCR could used wide-ranging systematic studies. alternative methods like amplification cDNA here provide promising comparative resolution fishes.