玻璃缺鳍鲶线粒体全基因组序列测定与分析

Sequencing and Analysis of Complete Mitochondrial Genome of Catfish Kryptopterus vitreolus

本文采用参照近缘物种线粒体基因组设计覆盖全基因组引物的方法构建并获得玻璃缺鳍鲶Kryptopterus vitreolus线粒体基因组全序列,分析其全序列特征和结构,为鲇形目鱼类的系统进化研究提供基础数据。结果表明,玻璃缺鳍鲶线粒体基因组全长16 662bp,碱基组成具有高AT含量的偏向性,结构组成和排列顺序和其他硬骨鱼基本一致,包括13个蛋白质编码基因、22个t RNA、2个r RNA和1个D-loop区。全基因组中除COX1以GTG为起始密码子外,其余12个编码蛋白的基因都以ATG开头。7个编码蛋白基因(ND1、Cox1、ATP8、ATP6、ND4L、ND5和ND6)以TAA终止,其余6个编码蛋白的基因没有完整的终止密码子。对玻璃缺鳍鲶线粒体基因组D-loop区的终止序列区、中央保守区和保守序列区的结构分析,识别5个保守序列(CSB-1、CSB-2、CSB-3、CSB-D和CSB-E)和一个潜在的终止序列E-TAS。利用玻璃缺鳍鲶分别与其他4种鱼的线粒体基因组全序列及13个编码蛋白基因的核苷酸序列进行比对分析。结果表明,玻璃缺鳍鲶与南方鲇Silurus meridionalis同源性最高,5种鱼线粒体基因组中COX1基因相对最保守,相似度为78.98%~92.78%。基于5个科12种鱼与2个外群物种的线粒体控制区(D-loop区)的核酸序列构建的系统进化树表明:玻璃缺鳍鲶独自一支且与鲇Silurus asotus和南方鲇亲缘关系最近。

Kryptopterus fishes are relatively difficultly classified according to conventional morphological taxonomy due to various kinds and similar shape, and unclear phyletic evolution in some species. To provide basic data to the classification of fishes in Siluriformes, the complete mitochondrial genome of catfish Kryptopterus vitreolus was obtained by PCR based on 15 primers, which were designed on the basis of related species mtDNA sequences. The complete mitochondrial genome of the catfish is 16 662 bp in length, including 2 ribosomal RNA genes, 22 transfer RNA genes, 13 protein-coding genes, and a non-coding control region. The organization and location of genes in the mitochondrial genome of the catfish were consistent with fishes published in Gen Bank. In control region, 5 CSBs （CSB-1, CSB-2, CSB-3CSB-D and CSB-E）, 1 potential E-TAS and 1 poly-T region were identified, and 13 protein-coding genes of 5 species were aligned by Clustal W to study the conservation between and its relative species. The protein similarity of 13 pairs ofhomolog genes was ranged from 55.30% to 99.4%, and the whole genome sequence similarity ranged from 61.19% to 89.60%. The similarity of 13 pairs of homolog protein-coding genes revealed that COX1 had more mutations, K. vitreolus being the highest similarity with catfish Silurus meridionalis. The phylogenetic analysis of K. vitreolus from the level of mitochondria genome based on 12 species in 5 families, combined with 2 outgroups＇ mitochondrial D-loop sequences, indicated that it clustered closely with catfish Silurus asotus and most similar to catfish S. meridionalis.