Genetic Characteristics Of ACACA Gene And Its Effect On Milk And Meat Quality Of Yak

Acetyl CoA carboxylases alpha(ACACA)is a key rate limiting enzyme in the de novo synthesis of fatty acids,which plays an important role in the regulation of fatty acid biosynthesis.In this study,reverse transcription-quantitative PCR(RT-qPCR)and bisulfite sequencing were used to detect the tissue expression of ACACA gene and the methylation level of CpG island in PI promoter at subcutaneous adipose tissue of 0.5-and 4.5-year-old Tianzhu white yaks,and to investigate the expression level of ACACA gene and epigenetic mechanism in subcutaneous adipose tissue.In addition,PCR-SSCP method was used to detect the variation of ACACA gene PI,PIA promoter and intron5-intron6 regions in Gannan yak,Tianzhu white yak,Qinghai yak,Tibet yak and wild blood yaks.And to analysis the effects of the variation of ACACA gene on milk and meat quality traits and fatty acid content in milk.The results show that:(1)The expression of ACACA was different between tissues and ages in 13 tissues of Tianzhu white yak,which was highly expressed in liver,brain,longissimus dorsi muscle and kidney tissues of 0.5-year-old yak,and the expression in liver was significantly higher than that in other tissues(P<0.05).However,the expression level of subcutaneous fat and liver in 4.5-year-old yak was significantly higher than that in other tissues(P<0.01).The expression in the kidney of 0.5-year-old yaks were extremely significantly higher than that of 4.5-year-old yaks(P<0.01),but the expression of subcutaneous adipose,liver and testicular was significantly or extremely significantly less than that 4.5-year-old yaks(P<0.05 or P<0.01).(2)In subcutaneous adipose tissue,the 1st CpG island region(g.-795 bp to-193 bp)of the PI promoter region of the ACACA gene is highly demethylated and there is an age difference.The average methylation level of BSP-1 primer amplification zone in 0.5-year-old yaks is extremely significantly higher than that in 4.5-year-old yaks(P<0.01).0.5-year-old yaks BSP-1 primer amplification zone CpG11,CpG31,CpG35,CpG37 site and BSP-2 primer amplification zone CpG5',CpG13',CpG15',CpG27',CpG28'site methylation level significantly or extremely significantly higher than 4.5-year-old yaks(P<0.05 or P< 0.01);The level of methylation in the 1st CpG island region of the PI promoter was negatively correlated with the expression of the gene in subcutaneous adipose tissue.(3)The polymorphism of ACACA gene was rich in five groups of yaks.Variation of c.-410C/T,c.-337T/C and c.-149C/G were detected in PI promoter region,c.-29847G/A and c.471+24C/T in PIA promoter and intron5-intron6 region.The detection areas of ACACA gene belong to moderate polymorphism.(4)The variation of PI promoter region of ACACA gene in Gannan yak significantly affected the milk fat rate,the percentage of total solid matter,the content of C12:0,C14:0,C18:0,C20:1,SFA,MCFA,MUFA and other fatty acids in milk,as well as the carcass weight and muscle shear strength(P<0.05).The variation of PIA promoter significantly affected the milk protein rate,milk fat rate,fat free solid matter percentage,the content of C4:0,C18:3n9,C20:1,C18:0 and SFA in milk,as well as the muscle shear force,cooking loss rate and water loss rate(P<0.05).The variation of intron 5-intron 6 region significantly affected the lactose rate,the percentage of total solid matter,the content of C14:0,C18:1n9c,C16:0,C16:1,MUFA and LCFA in milk,and the percentage of cooking loss rate in muscle(P<0.05).This study revealed the tissue expression of ACACA gene and the methylation difference of PI promoter in subcutaneous adipose tissue of Tianzhu white yak of different ages,and evaluated the association between ACACA genetic variation of Gannan yak and milk,meat quality and fatty acid content in milk,which enriched the theoretical basis of molecular genetic research on fat deposition of yak.