秦川牛IRS-1基因多态性与体尺和肉质性状的相关性

Association of IRS-1 Gene Polymorphism with Body Measurement and Meat Quality Traits in Qinchuan Cattle

旨在研究秦川牛IRS-1基因外显子的多态性,及其与秦川牛体尺和肉质性状的相关性。选取384头同等饲养条件下的18～24月龄健康秦川牛母牛为研究对象,采用PCR-SSCP技术结合DNA测序技术检测IRS-1基因外显子上存在的SNPs位点,并将其与秦川牛体尺和肉质性状进行关联分析。经DNA测序发现,在IRS-1基因外显子的2 346(B1位点)和2 394bp处(B2位点)分别发生了G→A和C→G突变,经分析发现,分别为氨基酸序列第782处Glu和798处Leu的同义突变。通过SSCP带型分析分别出现CC、CD和AA、AB 2种基因型,均未检测出第3种纯合基因型;卡方检验显示,B1位点在所检测牛群中处于Hardy-Weinberg平衡状态(P>0.05),而B2位点则处于Hardy-Weinberg极度不平衡状态(P<0.01);且B1处CC基因型为优势基因型,C为优势等位基因,处于低度多态状态;B2处基因型AA为优势基因型,A为优势等位基因,处于低度多态状态;关联分析表明,B1位点不同基因型个体间在体斜长、腰角宽、胸围和眼肌面积方面差异显著(P<0.05),B2位点在腰角宽、胸深和背膘厚方面差异显著(P<0.05)。将2个突变位点合并基因型进行单倍型分析发现,双杂合基因型个体(ABCD)除背膘厚和肌间脂肪含量外其他所分析的各性状均显著高于其他基因型组合,且多标记位点的组合效应值高于单标记位点。结果提示,IRS-1基因对秦川牛体尺及部分肉质性状有显著的影响,可以作为秦川肉牛新品系培育早期选择的候选基因,其中组合ABCD可能是影响秦川牛体尺和胴体性状的最佳基因型组合。

The aim of this study was to study the polymorphisms on exons of IRS-1 gene and their association with several body measurements and meat quality traits in Qinchuan cattle. The polymorphisms on exons of bovine IRS-1 gene was detected by using PCR-SSCP and DNA sequencing technology. 384 Qinchuan cattle with 18 to 24 months old were selected and the polymorphisms of bovine IRS-1 gene and their associations with body measurements and meat quality traits were analyzed. Two SNPs on exons of bovine IRS-1 gene were identified： B1 site g. ＋2346 G〉A,Glu〉Glu; B2 site： g. ＋2394G〉A, Leu〉Leu. Two genotypes at each sites（ B1 site： CC and CD〉B2 site： AA and AB） were identified and homozygote DD and BB were not detected in the study. The result of X^2 test showed that B1 site was in agreement with the Hardy-Weinberg equilibrium （P〉0.05）, B2 site was significantly deviated from Hardy-Weinberg equilibrium （P〈 0.01）. At B1 site, genotype CC was dominant genotype, C was preponderant allele, the site belonged to intermediate genetic diversity. At B2 site, genotype AA was dominant genotype, A was preponderant allele, the site belonged to low genetic diversity. The result of association analysis demonstrated, at B1 site, individuals with different genotypes had significant differences in body length, hip width, chest circumference and loin-eye area （P〈0.05）, at B2 site, individuals with different genotypes had significant differences in hip width, chest depth and backfat thickness （P〈0.05）. Furthermore, haplotype analysis showed that body measurement traits of individuals with combined genotype ABCD were significantly higher than those of the other kinds of combinations except on backfat thickness and intramuscular fatty content. The effect of multi-loci combinations on individuals were higher than those of single-marker loci. As the result showed, IRS-1 gene had a significant effect on body measurement and carcass traits in Qinchuan cattle. Hence, it could be took as a candidate gene for selecting new breed of Qinchuan cattle and the ABCD genotype maybe the best one for the Qinchuan cattle breeding.