Study On Mitochondrial DNA Genetic Diversity Of 8 Cattle Breeds In China

Genetic polymorphism and origin study based on nucleotide variance in mtDNA D-loop region are a hot spot in bovine genetic study. MtDNA RFLP of mtDNA and nucleotide variance in mtDNA D-loop region have been intense studied aboard, while few domestic study was reported. In this study, we collected 33 samples of 8 bovine species, including Luxi cattle,Bohai black cattle,Xuanhan cattle,Hainan cattle,Xuwen cattle,Minnan cattle,Gannan cattle,Yanbian cattle from Shan-dong,Si-chuan,Hai-nan,Guang-dong,Fu-jian,Jiang-xi and Hei-longjiang Province respectively. We designed one pair seuquence specific primer and then obtained 910 bp sequence of D-Loop region by PCR. Then we aligned all these homologus sequence using Clustal W (version1.8) program. Further analysis may provide some evidence on bovine origin,divergence and diversity in China. Our results are presented as follows. 1. We detected 21 hyplotypes in 33 samples from 8 bovine species; averaged nucleotide content are: 28.5% for T, 24.9% for C, 13.6% for G and 33% for A. Average (A+T) content is 61.5 % and 38.5% for (G+C), which suggested excess of (A+T) in Chinese bovine D-loop region. 2. 7.78% of all nucleotide sites in D-loop region, 71 sites, are polymorphism in 21 hyplotypes. 61of these sites are transition, 7 of them are transvertion, 3 of these sites have both transition and transvertion substitution. 3. Nucleotide polymorhisms (p) in D-loop region of 8 bovine species are arranged from 0% to 3.23%, and hyplotype polymorphisms(H) are from 0 to 1. Among 8 bovine species, polymorphisms are low for Hainan cattle,Xuwen cattle,Gannan cattle,Yanbian cattle and p value is 0, 0.22%, 0.15% and 0.77& respectively; while is high in Minnan cattle,Bohai black cattle,Luxi cattle,Xuwen cattle and p value is 2.53%, 2.88%, 3.03% and 3.23% respectively. our result indicated ample polymorphism in 8 bovine population in china 4. we constructed phylogenetic tree of 8 species based on NJ method. Phylogenitic study indicated that bovine in china originated from mainly two maternal lineage: Bos Taurus and Bos indicus. Yanbian cattle,Bohai black cattle(SW10,SW15),Xuwen cattle(XH6,XH9),Luxi cattle(SJ8,SJ27) belonged to the Bos taurus lineage; while Xuanhan cattle (XH7),Xuanhan cattle(LZ16),Luxi cattle(SJ5,SJ12,SJ19),Gannan cattle(T11,T23),Hainan cattle(HN1),Minnan cattle(MN4,MN5) origined from Bos indicus. 5. It would be reasonable to use nucleotide diversity as a scale for bovine genetic divergence. Bos taurus and zebu originated separately, which would be a cause of low p value in these bovine population. Chinese north cattle,Yanbian cattlefor example, originated from Bos taurus ;Chinese south cattle, including Hainan cattle,Xuwen cattle and Gannan cattle diverged from Bos indicus, which would be reasonable for low p value in these populations.