Phylogenetic Study And Intron Gain Or Loss Of Hsp23and Hsp27Genes In Melanogaster Species Group

Drosophila melanogaster species group subjects to Genus Drosophila, Subgenus Sophophora, including not less than180species, most of which have been classified into12subgroups depended on morphologic characters. So far, though many studies about the phylogeny relationships of the melanogaster species group have been accomplished by quite a few approaches, its taxonomy and phylogeny are still controversial, due to multiple troubles.Nucleotide sequences of23species’Hsp23gene and Hsp27gene within the melanogaster species group were determined through the direct sequencing method. The sequences were aligned, and were tested for substitution saturation etc. The molecular evolution results presented high ratios of Ks/Ka and GCIII contents which imply that the coding regions are undergoing purification selection. During the phylogenetic analysis, Drosophila pseudoobscura and Drosophila persimilis are selected as outgroup. Phylogenetic trees are reconstructed by Neighbour-joining (NJ), Maximum likelihood (ML) and Bayesian method. The result shows that the melanogaster species group are clustered into three main lineages. Ananassae subgroup was firstly splitted. In the melanogaster subgroup, the analysis reveals that seven species can be separated into two clades:the first clade consisted of D.sechellia, D.melanogaster, D.mauritiana and D.simulans, D.mauritiana and D.simulans are the most closely related species. D.erecta, D.teissieri and D.yakuba form the second taxonomic clade. A novel intron gain or loss is observed in Hsp27gene of ananassae subgroup. Because the expression and function of heat shock protein is distinctive, this region may include abundant precious information for intron evolution and study of function.