Diversity, Phylogenetic Relationship And MtDNA Heteroplasmy Of Major Bactrian Camel Populations In China

China is a country with the richest Bactrian camel resources all over the world.Bactrian camel once played an important role in culture exchange, economic development and desert animal husbandry in the history. However, there has been no intensive study on genetic diversity and origin of Chinese Bactrian camels.In this study, two kinds of molecular markers including autosomal microsatellites and mitochondrial DNA D-loop sequences were used to analyze the genetic diversity and origin of 10 Bactrian camel populations from China and Mongolia.At the same time, mtDNA sequence heteroplasmy was discovered in Bactrian camels for the first time and the heterophlasmy polymorphism was examined and analysed in 10 Bactrian camel populations.1.Genetic variability and relationship for 452 individuals from nine indigenous Chinese and one Mongolia Bactrian camel populations were estimated using 18 mircrosatellite markers.Genetic parameter analysis showed that there was rich genetic diversity in 10 Bactrian camel populations. Average number of effective alleles was 4.18,a total of 242 alleles were observed across all the10 populations with mean number of alleles per locus as 13.44.The mean observed heterozygosity (Ho) was 0.5528 and average value of PIC was 0.5996.2. The analysis showed that genetic differentiation reached very significant level(P<0.001),9.6% of the total variance was present among populations and 90.4% was detected within populations.Cluster analysis showed that the 10 bactrain camel populations were divided into two groups, which were generally in agreement with geographic distribution.3. A total of 205 individuals from 10 populations were sequenced and analyzed for their mtDNA D-loop region.Seventeen polymorphic sites and 21 haplotypes were discovered from 940 bp long sequences.Further analysis revealed that the bactrain camels were more conservative than other domestic animals in terms of their limited mtDNA diversity. Phylogenetic analysis and network analyses showed that only one haplogroup present in 9 Chinese Bactrian camels populations and one Mongolia Bactrian camel population. Over 80% individuals belonged to three predominate haplotypes.Together with the 86 sequences retrived from the GenBank, a total of 286 sequences were finally analysed. The results showed same patterns of phylogenetic and network relationships.4. The mtDNA heteroplasmy was first found in the Bactrian camels.A series of tests were investigated to eliminate the false positive results from PCR amplification. MtDNA heteroplasmy was investigated through cloning and sequencing procedures to describe their types and characters.BLAST searching and analysis of heteroplasmy segment among individuals initially eliminate the false positive result from Numts (nuclear mitochondrial-like sequences). MtDNA heteroplasmy population analysis among the different populations showed that 99.2% individuals were heteroplasmic.Cluster analysis based on mtDNA heteroplasmy segment showed that a similar genetic relationship among the Bactrian poulations as revealed by autosomal microsatellites analysis. The presence of heteroplasmy increased mtDNA D-loop polymorphism of Bactrian camel.