Molecular Evolution Study On 18S RRNA Gen Of Taxus

As the development of bioinformatic, molecular evolution has become a hot deductive field of molecular biology. Base on molecular evolution, many molecular biologists go along the research of molecular evolution machanism and estimate the divergence time of some important species, nowadays. For the molecular evolution study on 18S rRNA gen of taxus, a program has been programmed based on perl and bioperl,to retrieve abundant 18S rRNA gen sequences of taxus and its' relative species from GenBank. After the multiple sequence alignments of 18S rRNA gen sequences, and a phylogenetic data set will be extracted for phylogenetic analysis. Based on the result of phylogenetic analysis, the relative-rate test,branch-length test and two-cluster test had been done and a linearized tree had been constrcuted then. At last, the average distance(branch length) and the divergence time between sister groups had been estimated.This study makes some conclusions as follow:1.The xl is the taxus chinensis in Xian Ning, as the study showes, xl and taxus chinensis passed through the relative rate test, and they have little diversity.2.As fossil evidences show, the fossil of taxus were found in the upper Cretaceous period. Moreover,the archaeology evidence of Xian Ning showes the taxus chinensis in Xian Ning is the Tertiary plant.In this study, the divergence time between taxus mairei and taxus chinensis is 57±21.4Ma ago, and it is consistent with the evidences above.3.As this study showed, the cell and taxus x media is faster than the xl and taxus chinensis in molecular evolution.This study supposes the manual interference such as cell culture maybe quicken the genetic variation.4.The program programmed in this study retrieved abundant 18S rRNA gen sequences from remote database--GenBank,it advantages the study base on mass sequences.5.For the test of molecular clock, this study points out the use of relative-rate test,branch-length test and two-cluster test together can improve the estimation of molecular clock.