Phylogenetic Study Of Easter And Orange Genes And Intron Gain Of Orange Genes In Melanogaster Species Group

Drosophila melanogaster species group subjects to Diptera Drosophilidae Genus Drosophila, Subgenus Sophophora, and it is the largest species group of Drosophilidae, including more than180species, most of which have been classified into12subgroups based on morphological characteristics. So far, several researches about the phylogeny relationships of the melanogaster species group have been done based on morphology, biogeography and molecular biology characteristics. However, because of the lack of information, the phylogenetic relationships among the species group remains controversial.This study determines primary sequences of23species of easter gene and20species of orange gene within the melanogaster species group. Moleculer evolution results show that the coding regions of the two genes undergo neutral selection, as the datas show that Ks/Ka value is approximately equal to1and GCIII contents is approximately equal to50%. Indel is observed in the intronl,2of the orange gene, so this region includes abundant informations of the phylogenetic relationships of the species.Drosophila persimiliswas selected as the outgroup, phylogenetic trees are reconstructed based on the sequence data of easter and orange genes with Neighbour-joining (NJ), Maximum likelihood (ML) and Bayesian method. The result shows that the melanogaster species group are clustered into three main lineages which is to hold identical views with morphological classification and most researches:ananassae subgroup is firstly divergented; the second is the montium subgroup; finally, suzukii-elegans-ficusphila-eugracilis-takahashii-melangaster is divergented. The relationships of the third lineage are different in our reseach of the melangaster subgroup:the reseach about easter gene shows that the oriental subgroup is divergented before the melangaster subgroup, on the contrary, the reseach about orange gene shows the oriental subgroup is divergented after the melangaster subgroup. D.melanogaster species complex is firstly divergented in the melangaster subgroup.andD.yakuba species complex and D.orena species complex follow D.melanogaster is firstly divergented in the D. melanogaster species complex.When amplifying the sequences of orange gene via PCR,we find a intron gain in the melangaster subgroup, relative to other seven drosophila,such as D.pseudoobsura, D.persimilis, D.willistoni, D.grimshqwi, D.mojavensis, D.repletides. The binding between intron and extron follow the"GT-AG" Principle strictly and the length of the new intron is56bp. The phenomenon illustrates same studes about montium group status are not supported but morphological classification. Rare genomic changes are valuable in phylogenetic study.