基于线粒体COⅠ和16S rRNA基因序列比较分析东海带鱼群体遗传多样性

测定了东海带鱼(Trichiurus lepturus Linnaeus)三个群体(命名为A: 122°32′E 29°55′N、B: 123°30′E 26°75N; C: 124°24′E 27°26′N)72个个体的线粒体DNA16S rRNA和COⅠ基因序列,通过单基因序列和联合序列分析, 研究了东海带鱼群体的遗传变异情况。分别得到1130 bp的COⅠ基因序列片段和554 bp的16S rRNA序列片段, 其中COⅠ基因片段的T、C、A、G含量分别为29.0%、28.9%、24.4%和17.7%; 16S rRNA基因片段的T、C、A、G含量分别为22.7%、27.6%、28.0%和21.7%。基于线粒体16S rRNA、COⅠ和16S+COⅠ基因序列分析, 72个个体中分别确定43个, 8个和49个单倍型, 存在单倍型共享现象。群体的单倍型多样性指数为0.9766—0.9992, 显示了群体内的单倍型较为丰富。3个群体间各序列平均核苷酸差异数(K)在5.111—9.024和0.0045—0.0076, 核苷酸多样性指数(π)为0.0048—0.0084, 显示不同带鱼群体遗传多态性丰富。使用邻接法构建的分子进化树揭示同一群体内大部分个体聚在一起。分析结果表明, 群体A遗传背景比群体B、群体C较为丰富, 群体内部个体差异大于群体间差异, 群体间基因交流频率较高, 遗传分化不明显, 初步判定东海带鱼3个群体的遗传多样性偏低。

A COMPARATIVE ANALYSIS ON THE GENETIC DIVERSITY OF TRICHIURUS LEPTURUS

Asingle gene fragment and combined nucleotide sequences for two gene fragments of mitochondrial DNA (mtDNA), which were 16S ribosomal RNA (16S rRNA) and cytochrome oxidase c subunit 1 (COⅠ), were analyzed for three populations of Trichiurus lepturus (T. lepturus, designated by A, B, and C). The length of 16S rRNA gene of mtDNA and COⅠ was 1130 and 554 bp, respectively. These two gene fragments were combined together to form a gene fragment with the length of 1684 bp for the purpose of subsequent genetic diversity analysis. The average contents of nucleotides T, C, A, and G were 29.0%, 28.9%, 24.4% and 17.7%, respectively in the mtDNA COⅠgene, while those mean contents were 22.7%, 27.6%, 28.0% and 21.7% respectively in 16S rRNA gene. In this study, 43, 8, and 49 haplotypes were defined in 72 individuals by using single and combined gene fragments, in which haplotypes were shared among the mentioned populations. The diversities of haplotypes varied between 0.9766 and 0.9992, indicating that the abundance of haplotypes was within different populations. The nucleotide differences and the nucleotide diversity in each population were in the ranges of 5.111—9.024 and 0.0045—0.0076, respectively. Genetic distances among the populations varied from 0.0048 to 0.00084. These results indicated that genetic diversity in three populations of T. lepturus was considerable. The construction of phylogenetic trees based on Neighbour-Joining (NJ) method showed that several individuals in the same population were aggregated. The achieved findings also indicated that high frequency of gene transfer among different populations resulted in low genetic differentiation. Population A contained richer genetic background than that of populations B and C. The difference within different populations was higher compared to among various populations. It could be concluded that the three mentioned populations of T. lepturus had low genetic diversity based on single and combined mtDNA genes.