The Polymorphisms Of AGPAT6 Gene And Their Association With Milk Traits Yield And Body Size In Xinong Saanen And Guanzhong Dairy Goats Breeds

In this study, we used bioinformatics, DNA sequencing, PCR-SSCP, CRS-PCR-RFLP and PCR-RFLP technique to investigate variations of all exons (total 12), part of the 5'UTR and 3'UTR region in AGPAT6 gene and their associations with body size traits (body height, body length, chest circumference); milk yield and milk composition (milk protein, milk fat, lactose and total milk solids non-fat solids, milk density) in 549 (Xinong Saanen and GuanZhong) dairy goats. The aim is trying to obtain the molecular genetic markers associated with economic traits, and providing the scientific foundation for dairy goat genetic resources conservation, development and utilization.The main results are listed as follow:1. Four SNPs from four loci (P1, P2, P4 and P10) of 10 loci (P1^P10) in AGPAT6 gene were detected in dairy goats, however, no polymorphism was found in remaining loci. Variations of the goat AGPAT6 gene were detected by DNA sequencing and PCR–RFLP methods. Four mutations (NC₀07328.3:g.152G>C, 8124G>A, 9263C>G, 16436G>A) were detected in 5'UTR (P1-KpnΙ), intron 2 (P2), exon 4 (P4) and 3'UTR (P10), respectively. No polymorphism was detected in remaining loci (P3, P5, P6, P7, P8, P9) of goat AGPAT6 gene.①The g.9263C>G mutation result in a synonymous genetic code of Threonine, in detailed, ACC (Thr) > ACG (Thr) at position 195 amino acid (aa) of the AGPAT6 (457 aa). There were three genotypes in the P1 locus of AGPAT6 gene: GG,GC and CC. The frequency of G/C allele was 0.936/0.064 and 0.955/0.045 in SN and GZ breeds respectively. At the P1 locus, both of the populations were low polymorphic (PIC<0.25) and not in the agreement of Hardy-Weinberg equilibrium.②There were three genotypes in the P2 locus of AGPAT6 gene: GG,GA and AA. The frequency of G/A allele were 0.694/0.306 and 0.819/0.181 in SN and GZ breeds respectively. At the P2 locus, both of the populations were moderate polymorphic (0.25<PIC<0.50) and GZ breeds is in the agreement of Hardy-Weinberg equilibrium and SN breeds is not. frequency of C/G allele was 0.793/0.207 and 0.746/0.254 in SN and GZ breeds respectively. At the P4 locus, both of the populations were moderate polymorphic (0.25<PIC<0.50) and not in the agreement of Hardy-Weinberg equilibrium.④There were three genotypes in the P10 locus of AGPAT6 gene: GG,GA and AA. The frequency of G/A allele were 0.729/0.271 and 0.623/0.377 in SN and GZ breeds respectively. At the P10 locus, both of the populations were moderate polymorphic (0.25<PIC<0.50) and GZ breeds is in the agreement of Hardy-Weinberg equilibrium and SN breeds is not.2. Siginficant association between the different genotypes of P4 locus of AGPAT6 gene and milk traits of dairy goats was found. The association between different genotypes of P1, P2, P4 and P10 loci and economic traits were analyzed in two dairy goat breeds using the SPSS (16.0) software and adopting the least square linear fitting method. The results showed that no significant association between different genotypes of P1, P2 and P10 loci and body size, milk yield and milk components were found in two dairy goat breeds (P>0.05).In this research, we also revealed that no association between different genotypes of P14 locus and body size trait were found in two dairy goat breeds (P>0.05). The statistical results showed that the individuals with genotype GG have significantly higher milk yield (P<0.05) than genotype CC individuals in SN breed. In milk component traits, the individuals with genotype GG have significantly higher milk fat, milk protein content and milk yield (P<0.05 or P<0.01, respectively) than genotype CC individuals in two dairy goat breeds.So, siginficant association between the different genotypes of P4 locus of AGPAT6 gene and milk yield, fat and protein traits of dairy goats was found.In conclusion, P4 locus of AGPAT6 gene can be preliminarily considered as a candidate gene for economic traits breeding in dairy goats.