Study On Genetic Diversity Of MHC In Putian Black Duck

Putian Black Duck breeding has a long history in China and is widely distributed geographically. Putian Duck is a highly reproduction breed and is the only black-feature egg-laying duck found in China. It is included on the list of the National Poultry Genetic Resource Conservation Species. As a highly valuable genetic data repository, its social and economic significance to the mankind should not be underestimated. This paper is a study of the genetic diversity of Anpl-MHC I, Anpl-β2m and Anpl-MHCⅡexon2 in Putian Black Duck based on the PCR-SSCP method, with an aim to discover new alleles. The purpose of the study includes: firstly, to enrich the MHC genetic theoretical data in relation to Putian Black Duck and provide a theoretical basis for the protection of local varieties; secondly, to lay the foundation for the further study of the function of MHC gene pool and provide theoretical basis for disease-resistant breeding. My study has yielded the conclusions as follow:1. Anpl-MHCⅠe xon2, Anpl-MHCⅠe xon3 and Anpl-MHCⅡβexon2 in Putian Black Duck presented extensive polymorphism, among which the Anpl-MHCⅠexon2 demonstrated the highest polymorphism, and Anpl-MHCⅡβexon2, Anpl-MHCⅠe xon3 and Anpl-MHCⅠexon4 in a decreasing order, with their frequency of SNPs being 32.43%, 24.37%, 19.93% and 7.69%, respectively.2. The amino acid composition of MHC gene four loci in Putian Black Duck showed that Anpl-MHCⅠe xon2, exon4 and MHCⅡβexon2 had obvious hydrophobicity, which played a significant role in maintaining the structure and function of MHC.3. The frequency of coden usage of four loci in Putian Black Duck showed differences, namely there existed codon bias with the four loci.4. The result of PCR-SSCP analysis showed that Anpl-MHCⅠexon3 and Anpl-MHCⅡβexon2 each had 4 alleles while Anpl-β2m didn't display any diversity.5. The major nucleotide variance types of Anpl-MHCⅠexon3 and Anpl-MHCⅠexon4 were transition, but Anpl-MHCⅠe xon2 and Anpl-MHCⅡβexon2 were transversion. Only in Anpl-MHCⅠexon2 locus was the synonymous replacement rate higher than nonsynonymous replacement rate. Anpl-MHCⅠexon2 and Anpl-MHCⅠe xon4 had the higher content of GC at 59% and 63.8%, respectively. The content of GC in the third codon of Anpl-MHCⅠe xon2 and Anpl-MHCⅡβexon2 were 82.7% and 72.6%, which showed that the tow loci were under a great selection pressure. 6. The results of PIC,Ne and He of Anpl-MHCⅠe xon3 and Anpl-MHCⅡβexon2 in Putian Black Duck showed that the tow loci had low heterozygosity but high genetic diversity.7. The Hardy-Weinberg equilibrium analysis revealed that Anpl-MHCⅠe xon3 and Anpl-MHCⅡβexon2 in Putian Black Duck were in disequilibrium.8. The MHC gene clustering analysis of Putian Black Duck versus other species showed that the genetic distance between duck and goose was the closest in the poultry group.