Polymorphism Of Candidate Genes In Large White Pigs And Their Association With Growth Traits

This study used high-resolution melting(HRM)typing to detect polymorphisms of seven candidate genes in large white pigs,such as melanocortin-4 receptor(MC4R),cell division cycle protein 16(CDC16),leptin(LP),and pig growth hormone(pGH),aryl hydrocarbon receptor(AHR),prolactin receptor(PRLR)and 3-phosphoinositide dependent protein kinase-1(PDK1),and the polymorphism was correlated with the growth traits of large white pigs.In the experiment,246 large white pigs were used as research objects.The DNA of the ear tissues were extracted by DNA extraction kit.Firstly,20 small white pig samples were amplified by PCR,and the polymorphic sites of the candidate genes were screened by direct sequencing.The HRM-specific primers were designed for the polymorphic loci.The polymorphism of 226 large white pig population samples was detected by HRM method,and the results were correlated with the production data.The results showed that there was a 2207A>G mutation site in the first exon of MC4R gene,a 837T>C mutation site in the exon 18 of CDC16 gene,a 3469T>C mutation site in the second exon of LP gene,and pGH,the exon 5 of the gene showed 1856C>T and 1917C>T mutation sites,the exon 10 of the AHR gene showed the 38332C>T mutation site,the exon 8 of the PRLR gene showed the 825A>G mutation site,and the 8881C>T mutation site in exon 6 of PDK1 gene.There are two alleles in the above polymorphic loci.In addition to the 18th exon of the CDC16 gene,there are two genotypes.The other six genes can be divided into three genotypes.The ?2 suitability test showed that the genotype frequency and allele frequency of MC4R gene,CDC16 gene and PRLR gene were not significantly different between the two populations,which was consistent with Hardy-Weinberg equilibrium law(P>0.05).The genotype frequency and allele frequency of LP gene,pGH gene,AHR gene and PDK1 gene were not significantly different in the small populations,which was consistent with Hardy-Weinberg equilibrium law(P>0.05),but the frequency distribution of the type frequency and the allele frequency were significantly different and did not conform to the Hardy-Weinberg equilibrium law in large population(P<0.05).According to the polymorphic information content(PIC)analysis,the alleles of MC4R gene,LP gene,pGH gene(1917),AHR gene and PRLR gene were all in moderate polymorphism(0.25<PIC<0.5),and the distribution of the alleles of CDC16 gene and PDK1 gene in these two populations is low polymorphism(PIC<0.25),and the distribution of two alleles of pGH gene(1856)in small populations is in low polymorphism(PIC<0.25),but the distribution in large populations is moderate polymorphism(0.25<PIC<0.5).The correlation analysis between polymorphism and growth traits showed that MC4R gene had a significant effect on body weight and daily gain(P<0.05).CDC16 gene was high in body height,body length,birth weight,weaning weight,and daily gain.There was a significant effect(P<0.05),LP gene had a significant effect on body length at 6 months of age(P<0.05),and pGH(1856)gene had a significant effect on 20-day weight and 2-month-old weight.(P<0.05),pGH(1917)gene had no significant effect on all measured growth traits.AHR gene had a significant effect on body height at 2 months,body weight at 6 months and daily gain(P<0.05).The PRLR gene had a significant effect on birth weight,20-day weight,weaning weight,6-month-old body weight and daily gain(P<0.05).PDK1 gene had a significant effect on body height at 6 months(P<0.05).In summary,these seven genes have certain effects on the growth and development of large white pig,and provide a reference for the modern molecular breeding of the subsequent white pork quality traits and growth traits.