Xiaofeng Wang , Nana Liu , Kongshu Ji

Key Laboratory of Forest Genetics & Biotechnology, Ministry of Education, Nanjing Forestry University, Nanjing, 210037, P.R. China
Author    Correspondence author
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.

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)

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.

Buxus spp; Chinese pearl boxwood; B. sinica var. parvifolia; ITS sequence; Molecular evolution; Nucleotide substitution