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Tree Genetics and Molecular Breeding 2012, Vol.2, No.2, 8
-
14
http://tgmb.sophiapublisher.com
8
A Letter Open Access
Molecular Evolutional Characteristics of the Plant ITS Sequences in
Buxus
Genus
Xiaofeng Wang , Nana Liu , Kongshu Ji
Key Laboratory of Forest Genetics & Biotechnology, Ministry of Education, Nanjing Forestry University, Nanjing, 210037
Corresponding author email:
ksji@njfu.edu.cn;
Authors
Tree Genetics and Molecular Breeding, 2012, Vol.2, No.2 doi: 10.5376/tgmb.2012.02.0002
Received: 20 Dec., 2011
Accepted: 17 Jan., 2012
Published: 14 Mar., 2012
This article was first published in Molecular Plant Breeding in Chinese, and here was authorized to translate and publish the paper in English under the terms of Creative
Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.
Preferred citation for this article:
Wang et al., 2012, Molecular Evolutional Characteristics of the Plant ITS Sequences in
Buxus
Genus, Tree Genetics and Molecular Breeding, Vol.2, No.2 8-14
(doi: 10.5376/tgmb.2012.02.0002)
Abstract
There are many plant species belonging to the genus
Buxus
. The taxonomy in the genus is far more confusing, especially
endemic to Chinese pearl boxwood (
Buxus
sinica
var.
parvifolia
), a rare endangered species in China, which remains controversial in
phylogenetics and classification yet. In this research, we chose five plant species in the
Buxus
genus and five populations of
endangered Chinese Pearl boxwood (
Buxus
sinica
var.
parvifolia
) to analyze rDNA ITS sequences. By combining the other nine
species of
Buxus
genus reported in the GenBank and using ITS sequence of
Pachysandra
terminalis
as reference, we did alignment
analysis for the ITS sequences of 18 species of the
Buxus
genus. The results indicated that nucleotide substitution in ITS sequences of
Buxus
plants should be far more transition occurring than transversion being. In the region of ITS-1, the numbers of bases transiting
are almost similar as that of bases transversing, while in the region of ITS-2 the numbers of base transiting are more than that of base
transversing and the same situation takes place in the region of 5.8S. However, the ratio of base substitutions in the regions of ITS-1
and ITS-2 or 5.8S did not reach significant difference based on the calculations following the Juks & Cantor’s One Parameter Model
and Kimura’s Two Parameter Model in statistics. The values of the ratio calculated by Two Parameter Model were a little bit larger
than that by One Parameter Model due to transition took place more than transversion happened in the region of ITS-2. Based on
detecting the relative rate of molecular evolution of different clustering groups in Genus
Buxus
, the results presented that there was
an obvious difference of molecular evolution rate of ITS sequences among the clusters in
Buxus
plants. In this study, it suggested that
Chinese Pearl boxwood (B.
sinica
var.
parvifolia
) should be a sister species instead of a variant of B.
sinica
according to the relative
rates of detection and phylogenetic analysis. Furthermore, there was close genetic relationship between B.
sinica
var.
parvifolia
and
B.
henryi
.
Keywords
Buxus
spp
; Chinese Pearl boxwood; B.
sinica
var.
parvifolia
; ITS sequence; Molecular evolution; Nucleotide
substitution
Background
The
Buxus
is the largest genus in the family of
Buxaceae, representing approximately two-third plants
in this family. The texture of wood is known as
fineness, density and good looking, suitable for making
sculpture, art and other crafts. It is also commonly
used to be ornamental plants, which is a good tree
species for garden and landscape greening due to
strong resistance to cold. Some species in this family
containing boxwood alkaloids has an high medicinal
values for curing coronary heart disease, etc. However,
phylogenetic relationships and classification of species
in the genus
Buxus
are more confusing yet. There
were different descriptions for species recorded in
different flora, it is difficult to distinguish some
species with similar morphologies in the practical
application that would bring some trouble for scientific
research and practical cultivation. Endemic to Chinese
Pearl boxwood (
Buxus
sinica
var.
Parvifolia
), the
taxonomic status and phylogenetic relationship have
yet remained controversial.
Pearl boxwood was published as a variant of
B
.
sinica
(Zheng, 1980). Lin (2004) found that Pearl boxwood
had distinct differences in variety of phenotypes from
B
.
sinica
by studying specimens of Pearl boxwood.
Whereas Pearl boxwood was very similar with
B
.