蚂蟥和水蛭种间遗传变异和系统 关系的ITS序列分析

目的:为了阐明蚂蟥Whitmania pigra,水蛭Hirudo nipponia种间遗传分化系统关系.方法:运用TTS测序分析我国不同地区蚂蟥W.pigra、水蛭H.nipponia核糖体TTS碱基序列差异,用MEGA4.0软件中的MP法构建的分子进化树.结果:蚂蟥和水蛭平均总TTS序列长度在857.2～861.2 bp,其碱基A,T,G,C的平均分别为25.12%,28.28%,17.34%,29.29%.GC含量明显高于AT含量.通过对蚂蟥、水蛭TTS基因片段遗传特征的研究发现其种内变异很小,在14个群体中有45个位点发生转换.MP系统树将14个种群蚂蟥和水蛭分为两大类群.结论:蚂蟥和水蛭的变异类型可能为种内变异为主.同时发现,基于DNA序列的蚂蟥及水蛭的系统分类结果与分类学的分类结果不完全一致,可能是由TTS序列在进化过程中发生了少量位点的变异,如碱基之间的转换、颠换和缺失等造成的.

Analysis of genetic differentiation and phylogenetic relationship between Whitmania pigra and Hirudo nipponia based on ITS sequence

Objective : To evaluate the genetic differentiation and phylogenetic relationship between Whitmania pigra Whitman and Hirudo nipponia Whitman. Method : By the sequences of the rDNA internal transcribed spacer (ITS) the molecular phylogenetic tree was constructed by MP method using software MEGA 4.0. Result :The average length of ITS was 857.2-861.2 bp. The A, T, G and C contents in this fragment were 25.12%,28.28%,17.34%,29.29%, respectively. The GC content was higher than the AT content. Little sequence variation was observed in ITS gene fragments with in species, and transition in only 45 loci was revealed in 14 populations. 14 W. pigra and H. nipponia populations were clustered into 2 groups by MP phylogenetic tree. Conclusion : The results also showed that the intraspecific variation was dominated in variation types of W. pigra and H. nipponia. The classification result of W. pigra and H. nipponia and its adulterants based on DNA sequences are not totally consistent with those based on classification. It showed that a little of mutation of base in ITS sequences had occurred in the process of evolution, such as transition cites, transvertion cites among base or base gap.