| As the primary economic trait of dairy goats,milk production including milk yield,milk protein yield,milk fat yield,milk protein percentage and milk fat percentage is the main index for its economic performance.According to the current research,many scholars believe that milk production traits are not only controlled by minor-poly genes or QTL,but also are regulated by the major genes closely related to milk production traits.Thus,it is quite important to identify the functional genes or causal mutation sites of milk production traits for the molecular breeding of dairy goats.Therefore,this study uses whole genome sequencing technology in dairy goat milk production traits research to select regions or loci related to milk production traits,which is to provide molecular basis for marker assisted selection of dairy goat,and to provide reference for the molecular breeding of dairy goats.In this study,through the comparation of Toggenburg and Laoshan dairy goats with non-dairy goat population in the field of whole genome,189 genes are identified from the common 394 significant windows of Toggenburg and Laoshan dairy goats to improve the reliablity of highly differentiated genomic regions.Then,by combining the results of functional enrichment analysis with the results of previous studies on milk production traits,this study initially identifies 5 genes(EIF4G1?VPS13C?SREBF1?CCR2 and JARID2)closely related to milk production traits.Among them,EIF4G1 gene is involved in mTOR signaling pathway related to milk protein synthesis;VPS13C gene is associated with insulin levels(insulin plays an important role in the process of milk protein synthesis);SREBF1 genes relate to milk fat synthesis;CCR2 gene is located near the QTL associated with somatic cell score and JARID2 gene is located in the vicinity of SNP which is significantly related to milk protein content.At last,some SNPs which have large Fst value and more conservative in the evolution of species are selected to verify among other population,and to do association analysis with milk yield of the Laoshan dairy goats.In order to analyze the association among polymorphisms of the VPS13 C,EIF4G1 and JARID2 gene and milk production traits of dairy goat,Toggenburg and Laoshan dairy goats were selected as the experimental group,and Liaoning,Ritu,Bange,Nanjiang cashmere goats were used as the control group.In this study,polymorphisms of exon 10,33,16 and intron 10 of VPS13 C,exon 18,24 and intron 18 of EIF4G1 and intron 1,2,3 of JARID2 were tested by DNA sequencing method.The results showed that,among the polymorphic loci detected in exon 10,33 and intron 10 of VPS13 C,g.22885 C > A and g.72809 G > A caused the changes in amino acids.Association analysis showed that there were no significant correlation between the different genotypes of the five polymorphic loci and the average daily milk yield of Laoshan dairy goats.However,two common haplotypes were identified in all studied goat populations.Haplotype ACAG in LD block was dominant in dairy goat(63.7%)and segregated at higher frequency than that in non-dairy goat(21.2%),indicating that ACAG haplotype may have relation to the milk production performance of dairy goats.In addition,two polymorphic loci were found in exon 18 and 24 of EIF4G1 gene.Mutation g.12301 A > G resulted in amino acid change,and mutation g.9003 G > A did not cause any amino acid change.In Laoshan dairy goat,g.9003 G > A assumed two genotypes named AA and AG respectively.The association analysis of genotypes and average daily milk yield revealed that individuals with genotype AA were significantly higher than those with genotype AG(P = 0.021).However,the rest polymorphic loci had no differences in allele frequency between dairy and non-dairy goat populations.These findings suggested that VPS13 C and EIF4G1 gene could be the candidate genes of milk production traits in dairy goat,and the g.9003 G > A loci of EIF4G1 might be an effective molecular marker for milk performance of dairy goat. |
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