摘要：

为研究PPARA对绵羊肌内脂肪(IMF)沉积的影响及作用机制,寻找绵羊肌内脂肪沉积相关分子标记,以小尾寒羊(STH)和萨寒杂交(STH×SFK)F₁群体为研究对象,通过测定其肉品质,利用H&E染色和油红O染色比较2个绵羊群体背最长肌组织学结构及脂滴分布;利用qRT-PCR和WB技术检测PPARA mRNA水平和蛋白水平在不同群体间的表达差异,并分析PPARA基因与肌内脂肪的相关性;Sanger测序技术检测PPARA基因SNP位点以评估其作为绵羊肌内脂肪沉积相关遗传标记的可能性。结果表明:小尾寒羊剪切力和失水率极显著高于萨寒杂交,但是pH值极显著低于萨寒杂交,大理石花纹评分小尾寒羊低于萨寒杂交群体;组织学染色显示,小尾寒羊肌纤维较粗,排列紧密,肌内脂肪在肌纤维间隙集中分布;萨寒杂交肌纤维较细且结构松散,肌内脂肪在肌细胞间及肌纤维间隙均匀、广泛分布,含量更高;PPARA mRNA表达量小尾寒羊群体显著高于萨寒杂交群体,PPARA蛋白表达量小尾寒羊群体极显著高于萨寒杂交群体;相关性分析显示,PPARA基因表达量与绵羊脂滴面积比及pH值呈极显著负相关,与剪切力和失水率呈极显著正相关,与大理石花纹评分弱相关;Sanger测序结果分析显示,2个绵羊群体PPARA基因第2内含子T49885C、T50007C、G50013A、G50835A、G50942A及G51154C位置上发生碱基突变,但小尾寒羊群体未检测到C49885T突变。SNP遗传多样性分析显示,SNP位点群体纯合度均大于杂合度,在群体中处于中低度多态;除G50835A突变偏离了Hardy-Weinberg平衡,其余SNPs均符合Hardy-Weinberg平衡,遗传基础稳定。研究认为,PPARA基因对绵羊肌内脂肪沉积具有重要影响,可作为绵羊肌内脂肪性状选择的潜在分子遗传标记。

关键词: 绵羊, 肌内脂肪, PPARA, 多态性

Abstract:

The study aims to investigate the effect and mechanism of PPARA on intramuscular fat (IMF) deposition,and to search for molecular markers related to IMF deposition in sheep.The experiment was conducted using Small-tail Han sheep (STH) and a hybrid F₁ population between Suffolk sheep and Small-tail Han sheep(STH×SFK)as the research object.By measuring their meat quality,the histological structure and fat drop distribution of longissimus dorsi muscle of two sheep populations were compared by H&E staining and Oil Red O staining;qRT-PCR and WB techniques were used to detect the expression differences of PPARA mRNA and protein levels among different populations,and analyze the correlation between PPARA gene and IMF;Sanger sequencing technology was used to detect the PPARA gene SNP site to evaluate the possibility of using it as a genetic marker related to IMF deposition in sheep.The results indicated that the shear force and water loss rate of STH were significantly higher than those of STH×SFK,but pH was extremely significantly lower than that of STH×SFK,marble score of STH was lower than that of STH×SFK population;histological staining showed that STH muscle fibers were thick and tightly arranged,with IMF concentrated in the muscle fiber gaps,and muscle fibers were thin and loose in structure in STH×SFK,and IMF was evenly and widely distributed among muscle cell and muscle fiber spaces,with a higher content.The expression levels of PPARA mRNA in the STH were significantly higher than those in the STH×SFK population,and PPARA protein expressions of the STH were extremely significantly higher than those of the STH×SFK population.Correlation analysis showed that the expression level of PPARA gene was extremely significantly negatively correlated with sheep fat droplet area ratio and pH,extremely significantly positively correlated with shear force and water loss rate,and weakly correlated with marble score.Sanger sequencing results showed that base mutations T49885C,T50007C,G50013A,G50835A,G50942A and G51154C occurred in the second intron of PPARA gene in two sheep populations,but no C49885T mutation was detected in the STH population.The analysis of SNP genetic diversity showed that the homozygosity of SNP loci in the population was greater than the heterozygosity,and they were in a medium to low degree of polymorphism in the population;except for the G50835A mutation,all other SNPs were in line with the Hardy-Weinberg equilibrium,and with a stable genetic basis.It was believed that PPARA gene had an important impact on IMF deposition in sheep,and could be used as a potential molecular genetic marker for IMF trait selection in sheep.

Key words: Sheep, Intramuscular fat, PPARA, Polymorphism