Abstract：Abstract Diacylglycerol acyltransferase 1(DGAT1), considered as an important candidate gene for milk fat traits, plays key roles in triglycerides synthesis. The Bos grunniens milk has rich nutrition and higher milk fat. However, there are few studies on the genetic mechanism of dairy quality traits, because it is restricted by distribution, local environment, economy and production condition. In the present study, the tissue distribution of Bos grunniens DGAT1 mRNA and the genotype polymorphisms in 3'-untranslated region (3' UTR) and exon 8 of yak DGAT1 gene were detected by quantitative real-time PCR (qRT-PCR) and single strand conformation polymorphism (SSCP), and the associations of different genotypes and alleles with milk quality traits of Gannan yak were analyzed. The results indicated that the basal expression level of DGAT1 were relatively high in mammary gland, longissimus dorsi, heart and subcutaneous fat, relatively moderate in kidney, small intestine, large intestine, but low in spleen. At the c.*197 T>C locus, animals with genotype FF had higher milk fat rate than those with EE and EF genotypes (P＜0.05). And individuals with allele E had lower milk fat rate and total solids percentage than those with missing allele E (P＜0.01 or P＜0.05). The double-bases mutation c.691-c.692 AA>GC(K232A) was found in Gannan yak and Tianzhu white yak, the allele K was predominant, but those mutations were not detected in Qinghai yak and Wild-blood yak. The presence of allele K was beneficial to increasing the milk fat rate. The results suggested that 3'-untranslated region of yak DGAT1 gene may have a certainly genetic effect on milk quality traits. These results enrich the molecular genetic data for dairy quality traits of yak.
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