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.