Studies On The Population Genetic Structure And Molecular Evolution Of SLA-DQA Gene Exon 2 In Four Miniature Pig Breeds

Major histocompatibility complex (MHC) was the most polymorphism in gene system. Here 217 pigs were detected, the exon 2, partial intron 1, and partial intron 2 of SLA-DQA gene was studied by PCR-RFLPs and clone sequencing in Zang pigs(Tibet pigs), Hezuo pigs, Diannan Small-eared pigs and Bama miniature pigs. After the exon 2 of SLA-DQA gene was digested by EcoR I and Alu I, the results were showed that the genotype frequency of BB at EcoR I-RFLP site was more than that of AB, the genotype frequency of AA was the lowest in the four breeds. To the Alu I-RFLP site, the genotype frequency of MM was more than that of MN, and the genotype frequency of NN was the lowest in Zang pigs, Hezuo pigs and Diannan Small-eared pigs. There were little different between Bama miniature pig and the other three breeds.In Bama miniature pigs, the genotype frequency of MN was more than that of MM, and the genotype frequency of NN was the lowest at the Alu I-RFLP site. There were no significant difference between Gaoyuan group and Huanan group when compared the genetype frequencies of both sites by t-test. Considering the AA and AB genotype, there were no significant difference among the four miniature pig breeds. For BB genotype, there was significant difference between Zang pigs and Bama miniature pigs, whereas no significant difference among Zang pig, Hezuo pigs, Diannan Small-eared pigs. There were no significant difference among the Hezuo pigs, Diannan Small-eared pigs, Bama pigs. For MM genotype, there was significant difference between Zang pigs and Bama pigs, whereas no significant difference among Zang pigs, Hezuo pigs, Diannan Small-eared pigs. There were no significant difference among Hezuo pigs, Diannan Small-eared pigs, Bama miniature pigs. No significant difference were found among the four breeds for MN genotype. For NN genotype, there was significant difference between Hezuo pigs and Zang pigs, whereas no significant difference among the Hezuo pigs, Diannan Small-eared pigs, Bama pigs, the same as among the Zang pigs, Diannan Small-eared pigs, Bama pigs. The genotype frequency of BBMN was the most and the AANN was the least among the total nine PCR-RFLP pattern types of SLA-DQA gene in four miniaturepig breeds. There was no significant difference between Gaoyuan group and Huanan group for nine pattern types. For AAMM genotype, there was significant difference between Diannan Small-eared pigs and the other three breeds, whereas no significant difference among Zang pigs, Hezuo pigs, Bama miniature pigs. For BBMM genotype, there was significant difference between Zang pigs and the other three breeds, no significant difference among Hezuo pigs, Diannan Small-eared pigs, Bama miniature pigs. For BBNN genotype, there were significant difference between Hezuo pigs and the other two breeds such as Zang pigs and Bama miniature pigs, while no significant difference between Hezuo pigs and Diannan Small-eared pigs. There were significant difference between Zang pigs and Diannan Small-eared pigs, while no significant difference between Zang pigs and Bama miniature pigs. There was no significant difference between Diannan Small-eared pigs and Bama miniature pigs. For ABMM, AANN, ABNN, AAMN, ABMN, BBMN genotypes, there were no significant difference among four breeds.The results of j2 showed that two alleles (A and B) of EcoR I locus and another two alleles (M and N) of Alu I locus in the four breeds were fit with Hardy-Weinberg equilibrium except the two alleles (M and N) of Alu I locus in Hezuo pigs.Compared with the reported sequences, four novel alleles were seperated and nomenclatured based on the 37 cloning sequnces in the experiment. The result showed that the middle diversity of SLA-DQA exon 2, which haplotype (gene) diversity was 0.923, nucleotide diversity was 0.03707. The distribution of the pairwise no. of differences and the Tajima's test of neutrality proved that the population size were stabilization of the four miniature pig breeds. From the Neighbour-Joining tree of SLA-DQA gene, the Bama miniature pigs and Diannan Small-eared pig were first cluster in one branch, and then cluster withZang pigs, the Hezuo pigs were last cluster with Zang pigs.