四种三齿线虫核糖体ITS序列的比较分析及亲缘关系探讨

Comparative Analysis and Phylogenetic Relationships among Four Species of Genus Triodontophorus Based on Sequences of Internal Transcribed Spacer of Ribosomal DNA

对短尾三齿线虫（Triodontophorus brevicauda）、锯齿三齿线虫（T.serratus）、小三齿线虫（T.minor）和日本三齿线虫（T.nipponicus）核糖体内转录间隔区（ITS）序列进行扩增、测序和比较分析。基于ITS序列,采用最大似然法（ML）构建系统发生树,分析4种三齿线虫与其他圆线虫的亲缘关系。结果 4种三齿线虫ITS1、5.8S和ITS2序列大小分别为370~376 bp、153 bp和322~334 bp;4种虫体ITS1核苷酸同源性为88.4%~100%,5.8S为100%,ITS2为82.9%~97.8%;进化树中盅口科线虫和圆形科线虫各形成一个大的分支,但盅口科中微小杯环线虫聚集在圆形科这一分支中;小三齿线虫与日本三齿线虫,短尾三齿线虫与锯齿三齿线虫各形成一小的分支,两两亲缘关系较近,4种三齿线虫与盆口属和食道齿属的关系较圆线属近研究结果可为三齿线虫的遗传进化和分子鉴定提供参考。

The sequences of internal transcribed spacer （ITS） of ribosomal DNA of Triodontophorus brevicauda,T. serratus,T. minor and T. nipponicus were amplified,sequenced and analyzed. The phylogenetic relationships among four species of genus Triodontophorus and other Strongylids nematodes in the GenBank were re-constructed by using maximum likelihood（ML） based on the sequences of ITS. The results showed that the length of ITS1,5.8S and ITS2 of four nematodes of Triodontophorus sp. was 370-376 bp,153 bp,322-334 bp,while the nucleotide homology of ITS1,5.8S and ITS2 of these nematodes was 88.4%-100%,100%, 82.9%-97.8%,respectively. The phylogenetic tree was divided into two major branches,including Cyathostomidae and Strongylidae branches,but Cylicostephanus minutus in Cyathostomidae was located in the branch of Strongylidae nematode.T. minor and T. nipponicus were in one sister clade,and T. brevicauda and T. serratus were another one,which they had close relationships. The relationship of four nematodes with Craterostomum and Oesophagodontus was closer than that of Strongylus. These results laid a foundation for further study of the genetic evolution and molecular identification of the nematode of genus Triodontophorus.