云南绵羊mtDNA D-LOOP序列多态性研究

Analysis of the Genetic Diversity and Origin of Yunnan Sheep Based on Mitochondrial DNA D-Loop Sequences

采用PCR-SSCP技术与mtDNAD-Loop序列分析相结合的方法,对我国云南昭通绵羊、腾冲绵羊、宁蒗绵羊3个地方绵羊品种共134个个体进行mtDNA序列多态性及起源进化研究。PCR-SSCP分析显示,在云南的3个绵羊群体中检测到线粒体编码区的Cytb和ND2基因的2种单倍型A和B。根据不同的单倍型从3个绵羊群体中共筛选出23个样品进行了mtDNA D-Loop区克隆测序,系统发育分析揭示,云南绵羊mtDNA D-Loop序列单倍型分为支系A和支系B两大类。基于PCR-SSCP和D-Loop区序列的分析结果一致提示云南绵羊存在支系A和支系B两大母系起源,对云南绵羊进行mtDNA D-Loop序列多态性分析,结果发现线粒体D-Loop区系列单倍型多样度Hd为87.5%～100%;核苷酸多样度Pi为0.21～0.26;平均核苷酸差异数k为22.9%～36.8%。此结果揭示云南绵羊遗传多样性相对贫乏。对云南绵羊mtDNA D-Loop进行Mismatch分析和Tajima'sD值中性检验,结果显示,云南绵羊群体核昔酸差异数表现出完整的2个峰形,且经过中性检验不显著,由此推断云南绵羊在过去没有出现群体扩张,群体大小保持稳定。

Mitochondrial DNA （mtDNA） diversity of 134 individuals of three indigenous sheep breeds in Yunnan was analyzed by PCR-SSCP technology and mtDNA D-Loop sequences. The three indigenous breeds included Tengchong, Zhaotong, and Ninglang sheep. PCR-SSCP analyses revealed that two genotypes, A and B, of mitochondrial Cytb and ND2 genes were detected in the three indigenous breeds. The mtDNA D-Loop sequences of 22 individuals chosen from the three according to different genotypes were sequenced. Phylogenetic analysis indicates that two mtDNA lineages A and B are in Yunnan sheep. These results from PCR-SSCP and D-Loop sequences consistently indicate that Yurman domestic sheep are derived from two maternal origins of A and B. In addition, the D-Loop sequences analyses show that the Haplotype diversity varies from 87.5% to 100%, nucleotide diversity from 0.21 to 0.26, and average number of nucleotide differences from 22.9% to 36.8%. Polymorphism analyses show that genetic diversity in Yunnan sheep is poor. According to Fu＇s and Tajima＇s D test and mismatch distribution analysis, the three indigenous breeds have not been subject to population expansion, suggesting that the population of Yurman sheep be stable.