利用trnL-F序列分析杨属树种的系统发育关系

Phylogenetic relationship of Populus by trnL-F sequence analysis

对杨属4个派17个主要栽培树种及杂种共26个雌雄单株进行了叶绿体trnL-F间隔区序列的PCR扩增、回收和纯化,并分别克隆到pGEM-T载体中进行序列测定。结果表明:在杨树中基因trnL-F间隔区序列的长度为771～811bp,G+C含量为30.6%～31.9%;排序后的比对长度为857个位点,其中46个为变异位点,33个为系统发育的信息位点。以嵩柳和极地柳为外类群,分别用邻接法和UPGMA方法构建了杨属主要栽培树种的系统发育进化树。系统进化分析显示:1)白杨派能聚类形成一个单独分支,而黑杨派亚支与青杨、胡杨派亚支聚类形成另外一个主要的分支,其中胡杨派和青杨派不能区分开;2)青杨派的藏川杨独立于杨属其他种形成一个单独分支,而冬瓜杨却与白杨派聚类在一起;3)白杨派为单系起源,黑杨派和青杨派为多系起源,胡杨派可能也是多系起源。研究结果在分子水平上为杨属树种的起源和系统进化研究提供了证据,具有重要的理论意义和潜在的实践价值。

The DNA fragments of non-coding sequences of the chloroplast trnL-F were obtained by sequence specific PCR amplification for 26 samples,collected from 17 species or hybrids from four sections in Populus.The PCR products were isolated,purified and ligated to pGEM-T.Ligated products were transformed to Escherichia coli with DH5ɑ and positive clones were selected for sequencing.The results show that the length of trnL-F sequences ranged from 771 to 811 bp and the percentage of the G ＋ C was 30.6%--31.9% .The sequences were aligned and final sequences were 857 bp in length,which included 46 variable sites and 33 parsim-info sites.The phylogeny tree was constructed with the nearest neighbor algorithm and UPGMA methods,using Salix viminalis and S.polaris as the outgroup.Results showed that：1） all samples in the Section Leuce formed a separate clade,while Section Aigeiros, Tacamahaca and Turanga formed another main clade,in which the Section Tacamahaca and Turanga could not be clearly separated;2） in the Section Tacamahaca,P.szechuanica was independent from the other species of Populus and formed a separate clade,while P.purdomii was clustered with the Section Leuce;3） Section Aigeiros,Tacamahaca and Turanga were thought to be polyphyletic,except for the Section Leuce.The results provide molecular proof for studying the origin and phylogeny of Populus,which may be of theoretical significance and have potential application in practice.