Gao Yuan, Qiu Jian-Hua, Zhang Bing-Bing, Su Xin, Fu Xue, Yue Dong-Mei, Wang Chun-Ren
College of Animal Science and Veterinary Medicine, Heilongjiang Bayi Agricultural University, Daqing, Heilongjiang Province 163319, PR China.
College of Life Science and Biotechnology, Heilongjiang Bayi Agricultural University, Daqing, Heilongjiang Province 163319, PR China.
Exp Parasitol. 2017 Jan;172:18-22. doi: 10.1016/j.exppara.2016.11.005. Epub 2016 Nov 30.
Cylicocyclus nassatus is a common and important parasite in the large intestine of equine. In this study, the complete mitochondrial (mt) genome sequence of C. nassatus was determined and comparatively analyzed with Cylicocyclus insigne. The mt genome size of C. nassatus was 13,846 bp, 18 bp longer than that of C. insigne. The circular mt genome includes 12 protein-coding genes, two rRNA genes, 22 tRNA genes and two non-coding regions. All the genes are transcribed in the same direction and gene arrangement is consistent with that of gene arrangement 3 (GA3). The overall sequence difference between the two complete mt genomes was 10.7%. For the 12 protein-coding genes, the comparison between C. nassatus and C. insigne revealed sequence divergence at both the nucleotide (6.3-13.0%) and amino acid (0.8-6.6%) levels. The nucleotide lengths of the 12 protein-coding genes were the same, except for cox3 which was longer in C. insigne. Phylogenetic analysis based on the concatenated amino acid sequence of the 12 protein-coding genes was performed using all the Strongylidae nematodes of the horse available in the GenBank. Phylogenetic analysis showed that C. nassatus and C. insigne clustered together with very high nodal support and the genus Cylicocyclus was closer to the genus Triodontophorus than to genus Strongylus. The mtDNA data determined in this study provides novel genetic markers for further studies on the identification, population genetics and molecular epidemiology of the genus Cylicocyclus.
纳氏圆环线虫是马大肠中一种常见且重要的寄生虫。在本研究中，测定了纳氏圆环线虫的完整线粒体（mt）基因组序列，并与显著圆环线虫进行了比较分析。纳氏圆环线虫的mt基因组大小为13,846 bp，比显著圆环线虫长18 bp。环状mt基因组包括12个蛋白质编码基因、2个rRNA基因、22个tRNA基因和2个非编码区。所有基因均按相同方向转录，基因排列与基因排列3（GA3）一致。两个完整mt基因组之间的总体序列差异为10.7%。对于12个蛋白质编码基因，纳氏圆环线虫和显著圆环线虫之间的比较显示，在核苷酸（6.3 - 13.0%）和氨基酸（0.8 - 6.6%）水平上均存在序列差异。12个蛋白质编码基因的核苷酸长度相同，但细胞色素c氧化酶亚基3（cox3）在显著圆环线虫中更长。基于12个蛋白质编码基因的串联氨基酸序列，对GenBank中所有可用的马圆线科线虫进行了系统发育分析。系统发育分析表明，纳氏圆环线虫和显著圆环线虫以非常高的节点支持率聚集在一起，圆环线虫属与三齿线虫属的亲缘关系比与圆线虫属更近。本研究中测定的mtDNA数据为圆环线虫属的鉴定、群体遗传学和分子流行病学的进一步研究提供了新的遗传标记。
