Studies On The Structural Variation Of QTL Region On Chromosome 8 Related To Reproductive Traits Of Xiang Pig

Eight structural variation?SV?sites were identified based on the re-sequencing data of 6Xiang pig.,which were all located on the chromosome 8 of pig.The region of SV site overlaped the QTL region related with reproduction trait.In order to find out whether these SV have varietal specific distribution and influence on gene function,the distribution frequency of SV in Xiang pig population was studied by PCR method,and compared with Qianbei black pig and Kole pig.Comparison of radish pig and big white pig in Jiangkou The main findings are as follows:1.The PCR results showed that these 8 SV really existed.2.SV site of DKK2-I₁-sv91?91 bp?was located in the intron 1 of DKK2 gene and the QTL of the number of papilla and corpus luteum.The distribution of polymorphism in Xiang pigs had no significant difference between high and low yield population of Xiang pig,and the DI type average litter size of the second litter was 0.86 more than that of II type?P<0.01?.Two transcripts were detected in total mRNA of individual ovarian tissues with DI type.The results of five pig breeds genotyping showed that there was no DD type in Yorkshire pig.The D allele frequency of four Guizhou local pig breeds was significantly higher than that of Yorkshire pig.The results of q-PCR showed that the relative expression of the inserted type was higher than that of the deletion type,which suggested that the insertion of the DKK2-I₁-sv91 site might be beneficial to the gene expression.3.SV site of FSTL5-I₂-sv477?477 bp?was located in the intron 2 of FSTL5 gene,it was found that QTL region related to reproduction was the number of nipple and the volume traits of uterine.There were significant differences in genotype distribution among high and low yield populations of Xiang pigs?P<0.05?,and the DI type average litter size of the third litter was 0.97more than that of II type?P<0.01?.The results of five pig breeds genotyping showed that DD was predominant genotype in Qianbeihei pig and Yorkshire pig.No difference was found in the amplification of the adjacent exons to the three genotypic variation sites,however,it was found that three bases were inserted in exon 3.4.SV site of LCORL-I₄-sv426?426 bp?was located in the intron 4 of LCORL gene and QTL region related to reproduction was the number of luteal.There were three genotypes in the high and low yield population analysis of Xiang pig,and there was no significant difference in genotype distribution.In the type of DI individual testicular tissue of Xiang pig,only the deletion type transcripts were detected.I allele was dominant gene in Yorkshire pig,which was significantly higher than that of four Guizhou local breeds.The results of q-PCR showed that the relative expression of DD genotype was lower than that of type II?P<0.01?.It was speculated that the deletion of DKK2-I₁-sv91 locus might not be beneficial to gene expression.5.SV site of STPG2-I₆-sv295?295 bp?and STPG2-I₆-sv274?274 bp?were located in the intron 6 of STPG2 gene.The QTL region of this two SV site related to reproduction was early estrus age.In STPG2-I₆-sv295,three genotypes were detected and there was no significant difference in genotype distribution.Differential expression analysis of heterozygous samples of Xiang pig showed that the preferentially transcriptional deletion alleles were found in testicular tissues.The results of five pig breeds genotyping showed that there was no DD genotype in Yorkshire pig,the I allele frequency was significantly higher than that of four local breeds?P<0.01?.II type in STPG2-I₆-sv27 was not detected in Xiang pig.There were significant differences in genotype distribution and gene frequency of high and low yield populations of Xiang pig?P<0.05?.The results of genotype typing in 5 breeds showed that I allele in Yorkshire pig was significantly higher than that in four Guizhou local breeds?P<0.01?.6.SV site of MAN2B2-I₃-sv100?100bp?was located in the intron 3 of MAN2B2 gene,the QTL region related to reproduction was the litter size,luteal body and non-functional nipple.There were three genotypes in Xiang pigs.In the second litter,correlation analysis showed that there was weak correlation between the genotype of and litter size in MAN2B2-I₃-sv100?0<?<0.2?.And deletion had no effect on the expression of DI type individual transcripts.7.SV site of NELFA-I₁-sv40?40 bp?was located in the intron 1 of NELFA gene.The QTL related to reproduction was the number of luteal and litter size.Genotype distribution in Xiang pigs had no significant differences.The DD type average litter size of the third litter was 0.95 less than that of II type?P<0.01?.In the third litter,the genotype of NELFA-I₁-sv40 was weak correlation with the litter size?P<0.05?.The frequency of I allele in Yorkshire pig was significantly higher than that of Xiang pig,which suggested that I allele might be the dominant allele of litter size traits.8.SV site of NSUN7-I₁-sv283?283 bp?was located in the intron 1 of NSUN7 gene.The QTL related to reproduction was the number of luteal,litter size and early estrus age.Three genotypes were all detected in Xiang pigs,and there was no significant difference in genotype distribution.I allele frequency of Yorkshire pig and Qianbeihei pig was significantly higher than that of Xiang pig and Kele pig?P<0.01?.In summary,the results suggested that the SV site of DKK2-I₁-sv91,LCORL-I₄-sv426,STPG2-I₆-sv295 and STPG2-I₆-sv274 can be used as candidate marker for the identification of Yorkshire pig breed and four Guizhou local pig breeds.The insertion/deletion of DKK2-I₁-sv91and LCorL-I₄-sv426 sites may affect the gene expression,so they can be used as candidate sites for molecular breeding of Xiang pig..The MAN2B2-I₃-sv100 and NELFA-I₁-sv40 were correlated with litter size and could be used as potential genetic markers for pig breeding.