太湖新银鱼线粒体D-loop和Cytb片段序列结构与进化速率比较

共获得49个太湖新银鱼(Neosalanx taihuensis)个体的线粒体细胞色素b(Cyt b)全序列和控制区(D-loop)部分序列。所测线粒体D-loop部分序列长度变化范围为648～680bp,识别到位于前端的一个串联重复序列、一个终止相关序列(ETAS),3个中央保守区保守序列(CSB-F、CSB-E、CSB-D)及一个保守序列区保守序列(CSB-1),结构与其他鱼类的研究结果类似。太湖新银鱼线粒体Cyt b和D-loop片段的相对进化速率的比较研究结果表明,太湖新银鱼D-loop总的序列多态性位点的比例为0.83%,低于线粒体Cyt b部分总的序列多态性位点的比例(1.31%)。假设太湖新银鱼Cyt b基因平均进化速率相对值为1,贝叶斯(Bayes)MCMC模拟给出Cyt b基因的相对速率区间估计为1.000±0.131,而D-loop基因的相对速率为0.859±0.261,表明太湖新银鱼D-loop基因的进化速率低于Cyt b基因,同时,后验概率分布的变异方差也比较大。说明Cyt b基因比D-loop基因具有相对较高的进化速率,也相对更接近分子钟假设。因此,可以认为Cyt b基因比D-loop基因更适于太湖新银鱼种内及近缘种间相关分子生态及系统地理格局的研究。

Molecular Structure and DNA Substitution Rate of the Mitochondrial Control Region and Cytochrome b in Taihu Salangid, Neosalanx taihuensis

The structure and related substitution rate of mitochondrial DNA displacement loop (D-loop) region and cytochrome b (Cyt b) were comparatively analyzed through Bayesian MCMC simulation in present study. Based on the sequence analysis of mtDNA D-Loop 648 -680 bp, the D-Loop structure of this species is similar to that of other fish species containing the extended termination associated sequence domain ( ETAS) , the central conserved domain (CD) and several conserved sequence block ( CSB-F、 CSB-E、 CSB-D、 CSB-1 ) .According to comparative analysis of related substitution rate in Neosalanx taihuensis, the rate of polymorphic loci was lower in D-Loop (0. 83% ) than in Cyt 4(1. 31% ) and the interval estimation of related substitution rate is 1. 000 ±0. 131 in Cyt 4 and 0. 859 ±0. 261 in D-Loop, respectively, which indicated that the mutation rates of D-loop were slower than that of Cyt 4 with large variance of Bayes posterior density distribution in N. taihuensu. It provided evidence that the substitution rate of Cyt 4 is higher than that of D-Loop, and is more approximate to molecular clock hypothesis, which indicated that Cyt 4 might be more appropriate molecular marker than D-Loop in studies on molecular ecology and phylogeography for this species.