Fish growth hormone genes: Divergence of intron sequence in charrs of Salvelinus genus

Sequences of the two large introns (C and D) from two paralogous growth hormone genes, GH1 and GH2, were compared in eight charr species of the Salvelinus genus (Osteichthes, Salmonidae). It was demonstrated that the rates of intron divergence in these two genes were remarkably different. Introns in the GH1 gene appeared to be more conservative, while the rate of intron variations was considerably higher in the GH2 gene. These data suggest that noncoding regions of nuclear genes under the selective pressure. The lower congruence of phylogenetic scheme constructed based on an analysis of the GH1 introns compared to that based on the GH2 data, as well as with the traditional views on the evolution of charr species, also favors the supposition on differences in the forces and directions of the selective pressure on the introns.