白额纵沟纽虫(Lineus alborostratus Takakura)的线粒体基因组

Complete Mitochondrial Genome of the Nemertean Lineus alborostratus(Nemertea: Heteronemertea)

通过PCR扩增、测序获得白额纵沟纽虫线粒体基因组全序列并进行了生物信息学分析。白额纵沟纽虫线粒体基因组全长15 476bp,包含后生动物线粒体基因组典型的13个蛋白质编码基因、22个转运RNA基因、2个核糖体RNA基因和1个747bp的非编码区。除tRNA-Thr和tRNA-Pro基因外,其他基因均编码在重链上。基因组碱基组成具有AT偏向性,蛋白质编码基因偏好使用富含T的密码子。蛋白质编码基因的起始密码子均为ATG,终止密码子多为TAA或TAG,nad1、nad2、cytb基因具有不完全终止密码子T。预测的22个tRNA均具有典型三叶草结构。非编码区未发现在其他纽虫所报道的特殊茎环结构,但在nad4基因上发现有37bp的发卡结构。白额纵沟纽虫的基因排列、起始密码子、tRNA反密码子与Lineus viridis完全一致,两者rrnL和非编码区长度差别较大,前者具有较少核苷酸插入。

The complete mitochondrial genome of Lineus alborostratus was sequenced and binformation analysis was made. As seen in most metazoans, the genome （15476 bp in length） encodes 13 protein coding genes, 2 ribosomal RNA genes and 22 transfer RNA genes, and contains a 747 bp non-eoding region. All genes except two tRNAs （trnT and trnP） are encoded on a heavy strand. Nucleotide composition of the genome is biased toward A and T. The protein genes prefer to use the T-rich codons. All protein-cod- ing genes start with ATG and most of them stop by TAA or TAG. The genes had1, had2 and cytb appear to use T as an incomplete stop codon. All predicated 22 tRNA genes have the typical clover structures. Special stem-loop structure was not detected in the main non-coding region, but a 37 bp stem-loop structure was detected in had4 gene. The gene arrangement, initiation codons and anti-codons in L. alborostratus are identical to those of Lineus viridis. Lengths of rrnL and the non-coding region are obviously different between the two Lineus species. L. alborostratus bears fewer nucleotide insertions than L. viridis.