五种缘毛类纤毛虫遗传关系的ISSR研究

应用ISSR分子标记揭示了5种缘毛类纤毛虫(Carchesium polypinum,Epistylis chrysemydis,E.plicatilis,E.urceolata和Vorticella campanula)的遗传关系.从34个引物中筛选到13个多态性高的引物进行研究.得到的遗传距离(0.666 7～1.000 0)显示ISSR技术具有较高的分辨率.依据构建的UPGMA聚类树,V.campanula首先和其他种类分开;C.polypinum和E.chrysemydis聚在了一起;在3种Epistylis纤毛虫中,E.plicatilis和E.urceolata聚在了一起.对比由核糖体小亚基RNA基因序列构建的系统发育树,发现:1)ISSR引物在缘毛类纤毛虫基因组中可以得到多态扩增;2)C.polypinum与Epistylis的关系近于V.campanula,在缘毛类纤毛虫分类中,单生或群居是重要的系统发育特征;3)E.plicatilis和E.urceolata的关系近于E.chrysemydis.在Epistylis属纤毛虫中,柄的中空与否是一个有用的系统发育和分类特征.本研究表明ISSR方法在纤毛虫相近和相似种遗传关系研究中是一种新的有用方法.

GENETIC RELATIONSHIPS OF FIVE PERITRICHOUS CILIATES INFERRED FROM INTER SIMPLE SEQUENCE REPEAT (ISSR) MOLECULAR MARKERS

In this study, ISSR (inter simple sequence repeat) molecular markers were used to clarify genetic relationships of five peritrichous ciliates: Carchesium polypinum, Epistylis chrysemydis, E. plicatilis, E. urceolata and Vorticella campanula.From 34 primers, 13 polymorphic primers were selected and tested. The genetic distance values going from 0.6667 to 1. 0000 among the five species show the ISSR-PCR method has a high resolution. In the phylogenetic tree constructed with the unweighted pair group method using arithmetic averages (UPGMA), V. campanula was separated from other species firstly; C.polypinum and E. chrysemydis were closely related; in the group of Epistylis species, E. plicatilis and E. urceolata were first clustered together and then grouped with E. chrysemydis. These results were compared with the phylogenetic tree from the complete small subunit ribosomal RNA (SSrRNA) gene sequences. We found that: 1) ISSR primers can give the informative profiles in peritrichous ciliates; 2) C. polypinum has a nearer relation with Epistylis than V. campanula. The colonial or solitary status might be a more important phylogenetic character within peritrichs than the characters of stalk and the myoneme; 3) E.urceolata shared closer relationship with E. plicatilis than E. chrysemydis. The hollow nature of the stalk is a useful phylogenetic and taxonomic character in the genus Epistylis. This study demonstrated that ISSR-PCR method was a new useful method to reveal the relationships among related or similar species in ciliates.