Yatawara Lalani, Wickramasinghe Susiji, Rajapakse R P V J, Agatsuma Takeshi
Department of Environmental Health Sciences, Kochi Medical School, Oko, Nankoku City, Japan.
Mol Biochem Parasitol. 2010 Sep;173(1):32-8. doi: 10.1016/j.molbiopara.2010.05.004. Epub 2010 May 12.
In the present study, we determined the complete mitochondrial (mt) genome sequence (13,839bp) of parasitic nematode Setaria digitata and its structure and organization compared with Onchocerca volvulus, Dirofilaria immitis and Brugia malayi. The mt genome of S. digitata is slightly larger than the mt genomes of other filarial nematodes. S. digitata mt genome contains 36 genes (12 protein-coding genes, 22 transfer RNAs and 2 ribosomal RNAs) that are typically found in metazoans. This genome contains a high A+T (75.1%) content and low G+C content (24.9%). The mt gene order for S. digitata is the same as those for O. volvulus, D. immitis and B. malayi but it is distinctly different from other nematodes compared. The start codons inferred in the mt genome of S. digitata are TTT, ATT, TTG, ATG, GTT and ATA. Interestingly, the initiation codon TTT is unique to S. digitata mt genome and four protein-coding genes use this codon as a translation initiation codon. Five protein-coding genes use TAG as a stop codon whereas three genes use TAA and four genes use T as a termination codon. Out of 64 possible codons, only 57 are used for mitochondrial protein-coding genes of S. digitata. T-rich codons such as TTT (18.9%), GTT (7.9%), TTG (7.8%), TAT (7%), ATT (5.7%), TCT (4.8%) and TTA (4.1%) are used more frequently. This pattern of codon usage reflects the strong bias for T in the mt genome of S. digitata. In conclusion, the present investigation provides new molecular data for future studies of the comparative mitochondrial genomics and systematic of parasitic nematodes of socio-economic importance.
在本研究中，我们测定了寄生线虫指状丝虫完整的线粒体（mt）基因组序列（13,839bp），并将其结构和组织与盘尾丝虫、犬恶丝虫和马来布鲁线虫进行了比较。指状丝虫的线粒体基因组比其他丝虫线虫的线粒体基因组略大。指状丝虫线粒体基因组包含36个基因（12个蛋白质编码基因、22个转运RNA和2个核糖体RNA），这些基因是后生动物中常见的。该基因组的A+T含量高（75.1%），G+C含量低（24.9%）。指状丝虫的线粒体基因顺序与盘尾丝虫、犬恶丝虫和马来布鲁线虫的相同，但与所比较的其他线虫明显不同。指状丝虫线粒体基因组中推断的起始密码子为TTT、ATT、TTG、ATG、GTT和ATA。有趣的是，起始密码子TTT是指状丝虫线粒体基因组特有的，有四个蛋白质编码基因使用该密码子作为翻译起始密码子。五个蛋白质编码基因使用TAG作为终止密码子，而三个基因使用TAA，四个基因使用T作为终止密码子。在64种可能的密码子中，指状丝虫的线粒体蛋白质编码基因仅使用57种。富含T的密码子，如TTT（18.9%）、GTT（7.9%）、TTG（7.8%）、TAT（7%）、ATT（5.7%）、TCT（4.8%）和TTA（4.1%）使用频率更高。这种密码子使用模式反映了指状丝虫线粒体基因组中对T的强烈偏好。总之，本研究为未来具有社会经济重要性的寄生线虫的比较线粒体基因组学和系统发育研究提供了新的分子数据。
