菟丝子rDNA ITS序列的测定及分析

目的研究菟丝子rDNA-ITS序列特征。方法分别采用PCR产物直接测序法和克隆测序法,对菟丝子属7个种rDNA的ITS区(包括ITS-1,5.8S rDNA和ITS-2)进行序列测定。结果菟丝子属植物ITS序列总长度约为612 bp,GC含量分别为:ITS-1区53%~63%,5.8S rDNA 48%~55%,ITS-2区46%~56%;苜蓿菟丝子种内的3个地理种发现了3个变异位点。用NJ法构建系统发育树显示:含日本菟丝子Cuscuta.japonica的分支处于系统树靠近基部位置,与之亲缘关系较近的依次为中国菟丝子C.chinensis和杯花菟丝子C.cupulata;余下5个种的分支中田野菟丝子C.campestris和五角菟丝子C.pentagona合为一支,南方菟丝子C.australis和苜蓿菟丝子C.approximata合为一支。结论NJ法建立的发育树与形态学分类基本相符,为菟丝子属植物分类鉴定提供了重要的分子依据。

Determination and analysis of rDNA ITS sequences of Cuscuta

Objective To study the characteristics of the sequences of internal transcribed spacers(ITS) of ribosomal DNA(rDNA) from Cuscuta.Methods The sequences of rDNA ITS region(including ITS-1,5.8S rDNA and ITS-2) were determined from 7 species of Cuscuta by the direct or clone sequencing of PCR products.Results The results showed that the full length of Cuscuta ITS was about 612 bp,the GC contents of ITS-1,5.8S rDNA and ITS-2 were 53%~63%,48%~55% and 46%~56%(respectively,) and there were three variable sites found in 3 populations of C.approximata.The(phylogenetic) tree based on the neighbor-joining(NJ) method indicated that the branch including(Cuscuta.)japonica was in basal position of the phylogenetic tree,and C.chinensis C.cupulata had a close relationship with the tree successively.In the branches of other 5 species,one was consisted of C.campestris and C.pentagona,and another,of C.australis C.approximata.Conclusion The phylogenetic tree based on NJ method corresponds with the morphological classification,which provides an important molecular basis for the classification and determination of Cuscuta genus.