兰州鲇线粒体Cytb基因的克隆与序列分析

为克隆兰州鲇（Silurus lanzhouensis）线粒体Cytb基因全序列，根据欧洲鲇（Silurus glanis）线粒体基因全序列设计特异引物进行兰州鲇线粒体Cytb基因的PCR扩增，得到1138 bp兰州鲇线粒体Cytb基因序列。对兰州鲇和其他13种鱼的线粒体Cytb基因核苷酸和氨基酸序列之间进行同源性比较，结果显示具有较高的同源性，核苷酸同源性介于61.38%-91.12%，氨基酸同源性介于76.62%-95.52%。对兰州鲇、欧洲鲇、大口鲇（Silurus meridionalis）、鲇（Silurus asotus）、越南鲇（Silurus cochinchinensis）的Cytb基因之间进行碱基替代分析，结果显示兰州鲇Cytb基因与鲇之间替换率最低，值为8.87%，转换/颠换值为3.21；与越南鲇之间替换率最高，值为14.41%，转换/颠换值为1.83。对本文克隆的兰州鲇Cytb基因与王庆容等测定的兰州鲇线粒体Cytb序列进行序列差异分析，结果显示两者之间替换率为11.16%，存在127个变异位点，转换/颠换比为4.08，遗传距离为0.1230。由NJ法基于兰州鲇和其他13种鱼的Cytb基因序列构建的系统进化树，结果显示与传统的分类地位基本吻合。  

THE CLONING AND SEQUENCE ANALYSIS OF THE MITOCHONDRIAL CYTOCHROME b GENE OF SILURUS LANZHOUENSIS

To clone the sequence of the mitochondrial cytochrome b (Cytb) gene of Silurus lanzhouensis, we designed a specific pair of primers from the mitochondrial genome of S. glanis. The 1138 bp S. lanzhouensis Cytb gene was obtained after PCR. Then we compared the homology of the mitochondrial Cytb gene between S. lanzhouensis and 13 other species. The results showed that these species have high homology in Cytb gene. The homology value of the nucleotides was between 61.38% and 91.12%, and the value of the amino acids was between 76.62% and 95.52%. We also analyzed the nucleotides substitution of the mitochondrial Cytb gene among S.lanzhouensis, S.glanis, S.meridionalis, S.asotus, and S.cochinchinensis, and found that the lowest frequency of nucleotides substitution occurred between S.lanzhouensis and S.asotus with the value of 8.87%, and TS/TV was 3.21. The highest frequency was between S.lanzhouensis and S. cochinchinensis with the value of 14.41%, and TS/TV was 1.83. Qing-Rong Wang, et al. previously reported the sequence of the mitochondrial Cytb gene of S.lanzhouensis. Here we conducted the sequence difference analysis between our results and theirs. The results showed that the frequency of nucleotides substitution was 11.16%, there were 127 variable sites, TS/TV was 4.08, genetic distance was 0.1230. The phylogenetic tree of S.lanzhouensis and 13 other species constructed by NJ method was consistent with the traditional taxonomic results.