Screening of SNP loci of the taste receptor TAS1R3 gene in Guizhou local pigs and their association analysis with growth traits

【Objective】This study aimed to screen the single nucleotide polymorphism （SNP） loci of taste receptor TAS1R3 gene in Guizhou local pigs， investigate associations between population genetic characteristics and TAS1R3 gene， as well as body size traits， to provide candidate molecular markers for genetic improvement of germplasm resources of Guizhou local pigs.【Method】A total of 242 pigs of Guizhou local breeds （Congjiang Xiang pig， Qiandonghua pig， Jiangkou Radish pig， Guanling pig， and Baixi pig） were used as research objects. Nine pairs of specific primers were designed for all exons of the TAS1R3 gene for PCR amplification and sequencing. SNP loci of the TAS1R3 gene were screened to perform genetic analysis， linkage disequilibrium analysis， haplotype and diplotype analysis， association analysis， and prediction of the secondary structure of TAS1R3 gene mRNA for the screened SNP locus.【Result】Four missense mutation loci， g.63613635T>C， g.63614535G>A， g.63616733T>C， and g.63617113G>A， were found in Cong-jiang Xiang pig， Qiandonghua pig， Jiangkou Radish pig， and Guanling pig. Genetic analysis showed that the g.63613635T>C and g.63616733T>C were moderately polymorphic in Qiandonghua pig and Guanling pig. Chi-square （χ²） test showed that the genotype distributions of all four SNP loci did not deviate significantly from Hardy-Weinberg equilibrium （P>0.05）. Linkage disequilibrium analysis revealed strong linkage disequilibrium effects between the follo-wing SNP pairs： g.63613635T>C and g.63614535G>A， g.63614535G>A and g.63616733T>C， and g.63613635T>C and g.63616733T>C in Jiangkou Radish pigs； g.63613635T>C and g.63616733T>C， g.63613635T>C and g.63617113G>A， and g.63616733T>C and g.63617113G>A in Guanling pig. Association analysis indicated that in Congiang Xiang pigs， individuals with the TC genotype at locus g.63613635T>C had significantly greater body length and chest circumference than those with the TT genotype （P<0.05， the same below）； while individuals with the TC genotype at locus g.63616733T>C exhibited significantly higher chest circumference index， body length， and c compared to TT genotype individuals.【Conclusion】Four missense mutation loci are identified from four breeds of Guizhou local pigs. The loci g.63613635T>C and g.63616733T>C are moderately polymorphic in Qiandonghua pig and Guanling pig. Strong linkage disequilibrium effects are found in Jiangkou Radish pig and Guanling pig. Individuals carrying the diplotype H1H3 in SNP locus of TAS1R3 gene in Congjiang Xiang pigs are associated with superior body size traits. TAS1R3 gene has the genetic potential to influence growth traits in Guizhou local pig breeds. g.63613635T>C and g.63616733T>C， as well as their diplotype H1H3， can serve as references for subsequent marker-assisted selection.