4个品系西藏拟溞12S rRNA基因序列及其分子进化研究

Molecular phylogeny of four strains of Daphniopsis tibetana Sars based on mitochondrial 12S rRNA gene sequences

应用线粒体12S rRNA基因序列对4个地理品系的西藏拟溞(纳木卡错品系、色林错品系、班戈湖品系、赛里木湖品系)进行分子系统发育研究,并结合GenBank中7种相近溞类的12S rRNA基因序列探讨了西藏拟溞的分子系统进化关系。结果表明,在4个品系西藏拟溞的4条12S rRNA基因序列中,A、T、G、C的平均含量分别为31.9%、32.45%、17.33%和17.95%,A+T的含量64.35%,G+C的含量为35.28%,A+T的含量明显高于G+C的含量,符合节肢动物A、T含量高的特点。聚类分析结果表明,西藏拟溞和其他溞属枝角类动物有着明显的遗传差异,说明西藏拟溞在枝角类生物学研究中有其独特的地位。遗传多样性计算结果表明:在4个品系的西藏拟溞中,纳木卡错品系与色林错品系以及纳木卡错品系与班戈湖品系的遗传相似性均较高,达98%左右;班戈湖品系与纳木卡错品系间的遗传距离最小,仅为0.0126,班戈湖与赛里木湖间的遗传距离最大,为0.0199;与其他溞属枝角类相比较,4个品系西藏拟溞种内差异相对不明显,而与其他溞种间的差异显著,西藏拟溞有着较高的遗传多样性水平。研究表明,12S rRNA基因序列包含有可靠的进化信息,可作为西藏拟溞种类鉴定良好的分子标记,同时利用这种分子标记法从分子系统进化方面证明了Daphnia tibetana和Daphniopsis tibetana Sars应分属于不同的种。

The molecular phylogeny of four strains of Daphniopsis tibetana Sars（NMKC,SLC,BG and SLM） were studied based on mitochondrial 12S rRNA gene sequences.The molecular evolution of D.tibetana were dicussed by means of 12S rRNA gene sequence of the corresponding sequences of 7 other species of Daphnia Cladocera from GenBank.The results showed that the mean concentration of A,T,G,C for 4 strains D.tibetana of 12 SrRNA gene sequences were 31.9%,32.45%,17.33% and 17.95%,respectively.The base pair concentrations were 64.35% in A＋T and 35.28% in G＋C.These were accordance with feature of higher A,T concentration in Arthropoda animals.There were significant differences between D.tibetana and other species of cladocera,according to the results of genetic distance and using UPGMA cluster analysis in the Mega 4 software package procedures,indicating that D.tibetana has an unique position in the research of biology of Cladocera.The highest genetic similarity were between NMKC strain and SLC strain as well as between NMKC strain and BG strain,the genetic distance between NMKC strain and BG strain was the lowest in 0.0126,and highest was between SLM strain and BG strain in 0.0199.It was indicated that the interspecific difference was very significant,and the intraspecific difference is unconspicuous compared with other species of Daphnia suchas.All above shows that D.tibetana Sars has high levels of genetic diversity,and mitochondrial 12S rRNA can provide the reliable evolutionary information,and it can be used as molecular markers for phylogeny events.In addition,Daphniopsis tibetana Sars and Daphnia tibetana were proved to be different species in molecular aspects by this method.