大口黑鲈肌球蛋白重链基因SNPs的筛选及与生长性状的关联

肌球蛋白是肌肉细胞的重要组成成分,影响肌纤维的组成和肌肉生长。为了研究肌球蛋白重链(MYH)基因多态性与大口黑鲈生长性状的相关性,本研究采用PCR技术扩增得到编码区序列全长为9759 bp的大口黑鲈MYH基因,该基因包含37个外显子和36个内含子,编码1940个氨基酸。采用直接测序法在MYH基因上筛选到8个单核苷酸多态性标记(SNP)位点(A-305G、G-558C、A-2784C、A-2816G、T-4765A、C-6206T、C-6811T和G-6935T),有4个位于外显子上,其中2个属于同义突变。用SNa Pshot方法对从同批繁殖、同塘养殖的大口黑鲈"优鲈1号"群体中随机选取的430尾个体中各位点的基因型进行检测。结果显示,内含子上的A-2784C和A-2816G位点完全连锁,所有位点在大口黑鲈"优鲈1号"群体中的平均有效等位基因数、平均观测杂合度和平均期望杂合度分别为1.635、0.406和0.373,仅C-6206T、C-6811T和T-4765A位点的基因型频率分布符合Hardy-Weinberg定律。采用一般线性模型分析各位点与大口黑鲈生长性状之间的相关性,研究发现,C-6811T位点CC基因型个体的体质量和全长显著大于TT基因型,CC基因型个体的体高和尾柄长显著大于CT和TT基因型,其余位点不同基因型个体间的生长性状均不存在显著差异。C-6811T位点与生长性状显著相关,可作为大口黑鲈分子标记辅助育种的候选标记。

SNPs detection of MYH gene and its association with growth traits in largemouth bass (Micropterus salmoides)

Largemouth bass (Micropterus salmoides) is one of the primary cultured species in China, with annual production of 350 000 tons. Growth is one of the most crucial economic traits of all aquaculture species, but the molecular mechanisms involved in growth of M. salmoides are poorly understood. Investigation of the correlations between single nucleotide polymorphism (SNP) and growth traits can provide candidate markers for molecular marker-assisted selection. Hypothesis-driven candidate gene association analysis is directed at genes that have clear roles in controlling special traits. Myosin heavy chain (MYH) is the main component of skeletal muscle cells and affects muscle growth and development. In order to study the relationship between DNA polymorphisms of MYH gene and growth traits of M. salmoides in this study, the sequence of MYH gene coding region was obtained by PCR amplification method, which was 9759 bp in length. MYH gene contained 37 exons and 36 introns and encoded a predicted protein of 1940 amino acids. Eight SNP mutations were identified (A-305G, G-558C, A-2784C, A-2816G, T-4765A, C-6206T, C-6811T and G-6935T) in M. salmoides MYH gene using direct sequencing method. Among them, four SNPs were located in exons and two synonymous mutations happened. Eight SNP loci of 430 randomly selected Youlu No.1 M. salmoides individuals were genotyped by SNaPshot method. Genetic structure was analyzed by Popgene32 software. The results showed that the average effective number (N_e), average expected heterozygosity (H_o) and average observed heterozygosity (H_e) of these SNPs was 1.635, 0.373 and 0.406, respectively. Chi-square test showed that three SNP loci (C-6206T, C-6811T and T-4765A) were in Hardy-Weinberg equilibrium state in the Youlu No.1 M. salmoides population. A-2784C and A-2816G formed two haplotypes (A and B), and three genotypes (AA, AB, and BB) were observed. A general linear model was established for correlation analysis between different genotypes at SNP loci of MYH gene and various growth traits using SPSS19.0 software. At the position of C-6811T, individuals with the CC genotype had signifcantly greater values for body weight or total length than those with the TT genotypes. The individuals with genotypes CC had a greater value than the individuals with the genotype CT and TT in body height and caudal peduncle length. Other seven SNP loci were not significantly correlated with growth traits. The growth-related C-6811T locus could be a useful candidate molecular marker for M. salmoides molecular marker-assisted selection.