草鱼GH基因3′部分序列多态性与生长性状及肌肉成分的相关性分析

Polymorphisms of the GH gene 3′ partial sequence and their associations with growth traits and muscle composition in juvenile grass carp(Ctenopharyngodon idella)

为了解草鱼GH基因多态性与早期生长性状及肌肉成分的相关性,实验利用直接测序法从156尾草鱼GH基因的3′部分序列中共筛选到9个变异位点(分别命名为SNP1~SNP9:G2825A、G2914T、T2966G、A3002T、T3022C、A3301G、C3463T、C3547T、C3620T)。卡方检验结果显示,9个位点均未显著偏离Hardy-Weinberg平衡,且均表现为中等多态性(0.25<PIC<0.5);经连锁不平衡分析发现,SNP3、SNP4和SNP5位点为一组完美连锁不平衡,SNP2、SNP7、SNP9位点为一组完美连锁不平衡;GH基因3′部分序列5个位点单倍型分析共发现6种单倍型,其中Hap1(30.4%)所占的比例最高,Hap6(4.8%)所占比例最低。利用GLM及多重比较对草鱼GH基因中9个SNPs多态性与早期生长性状和肌肉成分进行相关性分析,发现SNP2和SNP3位点的纯合突变型在体质量、体长和粗脂肪性状上均显著高于野生型和杂合突变型;在双倍型分析时得出了相似的结果,同时含有SNP2和SNP3位点纯合突变的双倍型组合在生长和粗脂肪性状上均显著性高于其他组合。研究表明,草鱼GH基因中SNP2和SNP3位点与早期生长性状及肌肉成分存在显著性相关,可作为草鱼生长及肉质改良的候选辅助分子标记,并且为进一步对相关变异位点的功能验证奠定研究基础。

In order to comprehend whether the polymorphism of grass carp GH gene was associated with growth traits and muscle compositions, 156 individuals from Yangtze River were used in this study. Nine polymorphic loci were found in the GH gene 3′ partial sequence： G2825AG2914TT2966GA3002TT3022CA3301GC3463 T C3547TC3620T, which were named SNP1-SNP9 respectively. Nine loci were not significantly deviated from Hardy-Weinberg equilibrium based on Chi-square test（P〉0.05）, and performed moderate polymorphism（0.25〈PIC〈0.5）. The results of linkage disequilibrium showed that SNP3, SNP4, SNP5 were a set of completed linkage disequilibrium（r2=1） and SNP2, SNP7, SNP9 were a set of completed linkage disequilibrium（r2=1）.Haplotype analysis for five loci in GH 3′partial sequence revealed 6 haplotypes, which Hap1（30.4%） had the greatest proportion, Hap6（4.8%） had the lowest proportion. A general linear model and multiple comparisons were used to analyze the correlation between those single nucleotide polymorphisms（SNPs） and grass carp traits. The results showed that the body weight, body length and fat content of individuals with the homozygous mutant genotype at SNP2 and SNP3 were significantly higher than wide-type and heterozygous mutant genotype. Similar results were found in diplotype combinations analysis. The body weight, body length and fat content of combination with heterozygous mutant genotype at SNP2 and SNP3 were significantly higher than other combinations. The results showed that the polymorphism of SNP2 and SNP3 in grass carp GH gene had a significant correlation with growth traits and muscle composition（P〈0.05）, and it might have utility as markers for practical breeding programs for growth traits and muscle composition in grass carp. Meanwhile, we have laid a foundation for further research on the functional verification of the relevant mutation sites.