赤潮棕囊藻(Phaeocystis globosa)rDNA ITS区序列变异与二级结构分析

测定了南海球形棕囊藻香港株P1、P2和湛江株ZhJ1的rDNAITS区序列(含5.8srDNA),结合Gen Bank的13条同源序列,比对长度为904bp,变异位点271个,简约信息位点221个,平均(A+T)(34.5%)<(G+C)(65.4%).藻株P1、P2和ZhJ1序列存在变异位点20个,序列间相似性为97.9%～98.5%.ITS序列在种间和种内的解析度高于18srDNA和28srDNA基因;构建的NJ树、MP树、贝叶斯推断系统树的结构是一致的,不同种类的棕囊藻单独聚类,不同地理来源的球形棕囊藻混杂分布但相同地理来源的藻株多聚类在一起.RNA二级结构显示,不同藻种间5.8srDNA区结构基本一致,表现出属的特异性;ITS1、2区结构表现较大的种间差异,表明ITS区RNA二级结构可为棕囊藻分类鉴定提供有用的分子结构信息.

Analyses of sequence variation and secondary structure on rDNA ITS regions of the strains of redtide-caused harmful algae Phaeocystis globosa

Sequences of rDNA ITS region in the Strains P1,P2 and ZhJ1 of Phaeocystis globosa collected from Hongkong and Zhanjiang in South China Sea were determined.Combined with 13 homologous sequences downloaded from GenBank,the aligned ITS sequences of Phaeocystis(including 5.8srDNA) were 904bp,of which 271 sites were variable,and 221 sites were parsimony-informative,the contents of(A+T)(34.5%) were less than those of(G+C)(65.4%).20 sites were variable and no parsimony-informative sites were found in the sequences of P1,P2 and ZhJ1,sequence similarities were 97.9%-98.5%.The resolution to interspecific and intraspecific relationships in ITS sequences were better than 18s,28s gene.The topologies of phylogenetic trees derived from Neighbor-Joining memod,Maximum parsimony method and Bayesian inference were consistent.Different Phaeocystis speciesclustered independently.Although different geographical strains of the same Phaeocystis species might intertwine together,the strains of the same geographical origin strains tended to cluster.A comparison of secondary structures of rDNA ITS sequences revealed that the 5.8srDNA structures were basically the same in different species of the same genus, indicating the specificity of the genus;The secondary structure of the ITS1,2 regions were much different among species;indicating that the secondary structure of rDNA ITS region could provide some molecular structure information for the classification of Phaeocystis.