18S rRNA序列差异在马梨形虫分类学中的应用

18S rRNA sequence differences in the equine piroplasmid taxonomy in the application

为揭示18SrRNA V4高变区在物种分类学的本质意义,及进一步阐述马泰勒虫(之前称马巴贝斯虫)的分类学地位,本试验参考马泰勒虫(DQ287951)和驽巴贝斯虫(FJ209026)18SrRNA基因序列,在其V4高变区设计引物。将获得的片段克隆至pMD19-T进行测序,正确的结果与其他种梨形虫的相应序列进行分析。系统发生树结果显示,泰勒虫和巴贝斯虫处于明显的两个分支,而称之为马巴贝斯虫的物种和泰勒虫有着较为密切的关系,他们处于同一分支,其亲缘关系较巴贝斯虫更远。序列对齐分析表明,巴贝斯虫核苷酸序列相对于泰勒虫种序列存在多个位点的缺失和突变。而马巴贝斯虫和泰勒虫18SrRNA V4高变区核苷酸序列的相似程度较高,与巴贝斯虫在该序列上的差异较大。以上结果表明,泰勒虫种和巴贝斯虫种18SrRNA V4高变区核苷酸序列间的这种缺失和突变可作为泰勒虫和巴贝斯虫分类依据的本质因素之一。马巴贝斯虫应隶属于泰勒虫科,泰勒虫属。

To determine the character of 18S rRNA V4 hypervariable region on taxonomic and taxpnomic status of Theileria equi, the genes were compared with piroplasmida. According to 18S rRNA gene sequences of Theileria equi and Babesia caballi in GenBank, the primers were designed and were amplified by PCR. This sequences were cloned into pMD19-T vector and sequenced. The phylogenetie tree was structured about the sequence and other protozoan 18S rRNA V4 hypervariable region nucleotide sequence in GenBank. Theileria and Babesia are in different branches, but as Babesia equi has a relatively close re- lationship with the Theileria. Sequence alignment analysis showed, 18S rRNA V4 hypervariable region has multiple deletion and mutation between Theileria and Babesia. The deletion and mutation can be used for Theileria and Babesia classification. So B, equi should be classified a~ Thoilo~;;A~,~ ＂Pk~;l~;.