赤潮叉角藻18SrDNA和ITS区序列测定与分析

SEQUENCE DETERMINATION AND ANALYSIS OF 18S rDNA AND INTERNAL TRANSCRIBED SPACER REGIONS OF RED TIDE-RELATED CRERATIUM FURCA

采用PCR及克隆测序的方法 ,对 1 998年引发渤海赤潮的叉角藻 1 8SrRNA基因及rDNAITS区 (InternalTranscribedSpacerRegions)进行了序列测定与分析。并通过因特网从国际分子生物学数据库中获取甲藻另外 1 5个种的 1 8SrDNA序列 ,以Tetrahymenacorlissi作为外类群 ,分别采用Neighbor Joining和Fitch方法构建了甲藻较为一致和可靠的进化树图 ,探讨具有高度多样性和在分类上争议较多的甲藻各类群之间的形态与分子进化关系。结果表明 ,Prorocentrum(有 2个简单的壳板 )出现得较早 ,而大多数多甲藻目 (覆盖着多个壳板 )、裸甲藻目 (大多数不具壳板 )和膝沟藻目的成员较晚出现。另外 ,对叉角藻ITS区的分析表明 ,ITS区为高变区 ,是良好的分子标记 。

The sequences of 18S rDNA and ITS regions were determined from a red tide-related species Ceratium furca collected from Huludao City, Liaoning Province, in 1998. Sequence alignments over 1700 nucleotides of 18S rDNA of Ceratium furca and other fifteen representative species of dinoflagellates from Genbank have been analyzed in order to investigate phylogenetic relationships within this highly divergent and taxonomically controversial group. A coherent and convincing evolutionary tree was obtained, using Tetrahymena corlissi as the outgroup. The reconstructed phylogeny indicates that the early emergence of Prorocentrum panamensis (characterized by two thecal plates) preceded that of most Peridiniales, a large order of thecate species, whereas the unarmored Gymnodiniales appeared more recently, along with members of the Gonyaulacales. Our results also show that the internal transcribed spacer of rDNA had a high level sequence divergence, suggesting the sequence may be a well-suited target sequence for developing genus and species-specific oligonucleotide probes. These results provide new perspectives on proposed evolutionary trees for the dinoflagellates based on morphology, biology, and fossil records.