太平洋鳕线粒体全基因组测序及结构特征分析

ANALYSIS OF COMPLETE MITOCHONDRIAL GENOME SEQUENCES OF GADUS MACROCEPHALUS

通过二代基因测序技术获得太平洋鳕(Gadus macrocephalus)线粒体基因组全序列,对线粒体基因进行了注释,对其序列结构进行了分析。研究结果表明,太平洋鳕线粒体基因组全长16569 bp,共编码13个蛋白质,并且包含了22个tRNA, 2个rRNA以及1个D-Loop区。碱基组成存在明显的AT偏向和弱AT负偏斜现象。太平洋鳕线粒体在蛋白质编码基因中共有5种终止密码子,包含哺乳动物线粒体常见终止密码子AGG与AGA。除tRNA-Ser(GCT)基因缺失二氢尿嘧啶臂(DHU臂)外,其余tRNA均能形成典型的三叶草结构。D-Loop区只存在与终止结合序列区(Terminal associated sequences, TAS)和保守序列框(Conserved sequences blocks, CSB)功能类似的序列,并且出现17 bp的嘧啶序列。非编码区含有一段保守的控制轻链复制起始的序列(OL)及一段74 bp的基因间隔区。基于线粒体基因组全序列和Cytb基因,分别构建了鳕形目下几种鳕的进化树,结果为揭示太平洋鳕进化地位提供了重要依据。

The next-generation sequencing technology was used to obtain the whole mitochondrial genome sequences of Gadus macrocephalus.The mitochondrial gene was annotated and its structure was analyzed.The results showed that the circular genome was 16569 bp in length with typical mtDNA components.The mitochondrial genome encodes 13 proteins and 22 tRNAs,2 rRNAs and a D-Loop region.The base composition showed a tendency of high AT and AT weak negative skewness.There were five kinds of termination codon in the protein coding gene of G.macrocephalus mitochondria,including AGG and AGA which were commonly found in mammalian mitochondria.It was shown that most of the tRNA structures share the classical clover shape,but the tRNA-Ser(GCT)is unique because of a shortage of DHU.Two sequences with the functions of TAS and CSB,as well as 17 bp pyrimidine-rich sequences were found in D-Loop region.The non-coding region contains a conserved sequence controlling the initiation of light chain replication(OL)and a gene spacer with 74 bp.Based on the whole mitochondrial genome sequence and the Cytb gene,the phylogenetic trees were constructed separately with several cod fish that belong to Gadiformes.The results provide an important evidence to reveal the evolutionary status of the pacific cod.