黄杨属植物ITS序列分子进化特点分析

Analysis the ITS Sequence's Characteristic of Molecular Evolution in Buxus

黄杨属植物种类多,分类较为混乱,特别是中国特有种珍珠黄杨的分类地位和系统进化存有争议,鉴于此,本文选取黄杨属5种植物和珍稀濒危植物珍珠黄杨的5个居群,对其rDNA ITS序列分析,结合GenBank中报道的黄杨属其它9个种,以板凳果属顶花板凳果的ITS序列为参照,用成对比较的方法对黄杨属18种植物的ITS序列比较发现,黄杨属ITS序列的碱基替换情况是转换数大于颠换数,ITS-1区间碱基发生转换和颠换的数目基本相似,而ITS-2区间碱基发生转换的数目大于颠换数,同样存在于5.8S区。用朱克斯和坎托一参数模型和木村两参数模型对黄杨属ITS序列的替换率计算,无论是ITS-1、ITS-2还是5.8S序列都未达到显著差异。但由于ITS-2序列碱基的变化转换明显大于颠换,所以两参数模型计算所得结果大于一参数模型;对黄杨属不同聚类群分子进化相对速率检测发现,该属不同聚类群的ITS序列分子进化速率存在明显差异。本研究从相对速率检测和分子系统进化分析发现,珍珠黄杨并非瓜子黄杨的变种,而是属于姊妹种,并且发现珍珠黄杨与大花黄杨的亲缘关系相对较近。

There are many species in genus Buxus and its taxonomy is confusion,especially for the endemic Buxus sinica var.parvifolia which is a rare endangered species in China.In this paper,we analyzed molecular evolution characteristics of ITS sequences from 18 examples by sequence comparison method.There are 14 genus Buxus species and 5 plant populations of B.sinica var.parvifolia.Compared to the ITS sequence of Pachysandra terminalis,it indicates there are more transition ratios than transversion ratios that come into being in those ITS base substitution;In ITS-1 the numbers of base transition are almost same to base transversion;But there are more base transition ratio than base transversion took place in ITS-2 and 5.8S.There is not distinct difference of base substitutions in ITS-1,ITS-2 or 5.8S after calculated based on Juks Cantor＇s One Parameter Model and Kimura＇s Two Parameter Model in statistics.The numerical values calculated by Two Parameter Model are larger than by One Parameter Model,due to more transition ratio than transvertion ratio in ITS-2.The results from relative rate test showed that different clusters of Buxus had different base evolution rate based on different ITS sequences regions analyzed.It＇s found that the B.sinica var.parvifolia was not the variation of the B.sinica by Relative Rate Test and Molecular phylogenetic analysised,but both are sister species,also we found that it has closer genetic relationship between B.sinica var.parvifolia and B.henryi.