荷斯坦牛Nramp1基因遗传多态性及其与乳房炎相关性的研究

Genetic polymorphism of Nramp1 gene and correlation with mastitis in Holstein cattle

利用PCR-SSCP技术检测了344头中国荷斯坦牛Nramp1基因exon 11的基因多态性,并分析了其不同基因型与乳房炎及产奶量性状的关系。结果表明:实验群体发现3种基因型AA、AB、BB,其中A等位基因为优势等位基因,等位基因频率为0.767,而B等位基因频率则为0.233。经X^2适合性检验,群体处于Hardy-Weinberg平衡状态(P>0.05)。测序结果显示:扩增片段分别在200 bp(C/G)和254 bp(T/G)存在碱基突变,并导致了氨基酸改变,分别为丙氨酸替换为脯氨酸(A1a356Pro)、亮氨基酸替换为蛋氨酸(Leu374Met)。通过构建最小二乘线性模型,进行Nramp1基因多态性与产奶量、体细胞评分(SCS)的相关性分析表明,AA型个体的SCS最小二乘均值显著低于BB、AB型(P<0.05),而AA型、AB个体的产奶量最小二乘均值显著高于BB型(P<0.01,P<0.05),AA基因型可作为乳房炎抗性的优良基因型。因此,可将Nramp1作为奶牛乳房炎候选基因应用于分子标记辅助选择育种。

In this research, PCR-SSCP technique was used to analyze the polymorphisms of the exon 11 of Nrampl gene in Chinese Holstein cattle （n=344）, and correlation between polymorphisms of Nrampl with somatic cell score （SCS） and milk production traits was analyzed. The results show that three genotypes namely AA, BB, and AB were detected. Allele A was predominant and the frequencies of alleles A and B were estimated to be 0.767 and 0.233, respectively. Chi-square test indicated that the polymorphic locus in Chinese Holstein fitted Hardy-Weinberg equilibrium （P〉0.05）. Sequencing analysis showed two polymorphic sites at positions 200 bp （C/G） and 254 bp （T/G）, which resulted in amino acid alteration Ala356Pro and Leu374Met. The least squares means of SCS in Holstein cattle was lower for genotype AA than that for genotypes AB and BB （P〈0.05）. The least squares means of milk yield of genotype AA and AB were higher than that for genotype BB （P〈0.05, P〈0.01, respectively）. Genotype AA was beneficial to mastitis resistance. This suggested that Nrampl may be a candidate gene responsible for mastitis in Holstein cattle.