Study On The Evolution Of Mitochondrial Gene And BLB Gene In Four Swan Species

Swan is a kind of anserformes avain, belonging to anatide. The whooper swan (Cygnus cygnus), Tundra Swan(Cygnus columbianus) and mute swan(Cygnus olor) are three species in China, listed as classⅡ protected species. At present, most of swan study concentrate on morphology, breeding, breeding and disease prevention. With the development of molecular biology, more and more scholars focus on anserforme avian molecular studies. Using the mitochondrial genome reconstruction of phylogenetic tree solve the problem of the origin of species and classification. Through the determination of MHC genes found species of infectious disease resistance. More than twenty kinds of anserforme birds the whole sequence of the mitochondrial genome were measured. Many kinds of birds MHC Ⅱ sequence of such molecules was released. But the related research of swan is not much.In this study, we obtained whooper swan, tundra swan, mute swan and black swan BLB gene’s exon 2 and exon 3 sequences and then study the polymorphism of BLB gene, providing the theoretical information for Anseriformes MHC study and helping the study of disease prevention and control. Combined with mitochondrial genome sequences of all from the perspective of molecular study relationship between the evolution of the swan. The results are as follows:1. We obtained the complete mitochondrial genome of the whooper swan and mute swan, which lengths are 16721 bp and 16735 bp respectively. The order of the content of four bases is C>A>T>G, and content of AT is greater than GC. This result shows a clear preference for AT, and it is similarity with the known distribution of the bases in Anserinae.2. There are 3 introns and 4 exons in swan BLB gene sequences, including incomplete exon 1 and exon 4. The length of exon 2 is 270 bp, and exon 3 is 282 bp.3. The polymorphism of exon 2 is higher than exon 3 obviously.4. Exon 2 is affected by positive selection pressure while exon 3 is neutral choice. And exon 3 is more conservative in the process of evolution.5. Swan BLB exon 2 of the system in different evolutionary tree species crossover phenomenon, think the swan BLB genes across species in the course of evolution of evolution.In the evolution of the exon 2 build tree trends and mtDNA similar construction of the evolutionary tree.6. Based on the analysis of the classification of the alleles, it was concluded that there were at least 2 loci in the BLB gene of the whooper swan.5.6. In the evolutionary tree of swan BLB exon 2 crossover phenomenon appear different species, agree to that the swan BLB gene in evolution across species exist in the process of evolution.