| 普通小麦rDNA的ITS区及其基因组起源 |
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| 引用本文： | 钱锦,孙毅,段永红.普通小麦rDNA的ITS区及其基因组起源[J].作物学报,2009,35(6):1021-1030. |
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| 作者姓名： | 钱锦 孙毅 段永红 |
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| 作者单位： | 1.山西大学生物技术研究所，山西太原030006；山西省农业生物技术研究中心，山西太原030031；3山西农业大学，山西太谷030801 |
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| 基金项目： | 山西省科技基础条件平台建设项目 |
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| 摘 要： | 采用特异引物对普通小麦(Triticum aestivum L.) rDNA的ITS区片段进行PCR扩增并测序，通过邻接法聚类分析, 得到3种类型的扩增产物。结果表明，ITS区序列长度是602 bp，其中ITS1和ITS2分别有8个和20个变异位点，ITS区揭示的遗传分化距离变化范围为0~0.038,平均值为0.021。通过从GenBank搜索并下载普通小麦野生近缘种ITS序列与本研究获得的普通小麦ITS序列进行比对，并用MEGA、PAUP、PHYLIP软件分析，按Kimura-2参考模型计算分化距离，以旱雀麦(Bromus tectorum)为外类群邻接法构建聚类树。根据杂交后代具有亲本的ITS序列遗传特点，认为小麦形成较晚，尚未同步进化完全，从分子水平上为普通小麦是异源六倍体提供了证据。通过与其A、B、D基因组可能供体的ITS区序列进行比对分析发现各自有不同程度的变异，认为普通小麦在多倍体形成过程中发生了序列消除现象，结合我们提出的“同步进化”对于不同的基因或者说不同类型的DNA序列是不同步的假说，解释了无法找到真正供体的原因。综上所述，我们认为A、B、D基因组的原初供体可能分别是乌拉尔图小麦(T. urartu)、山羊草(T. speltoides)和节节麦(T. tauschii)。
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| 关 键 词： | 小麦 ITS序列 同步进化 |
| 收稿时间： | 2008-09-23 |
ITS Region of rDNA in Common Wheat and Its Genome Origins |
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| QIAN Jin,SUN Yi,DUAN Yong-Hong.ITS Region of rDNA in Common Wheat and Its Genome Origins[J].Acta Agronomica Sinica,2009,35(6):1021-1030. |
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| Authors: | QIAN Jin SUN Yi DUAN Yong-Hong |
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| Institution: | 1.Institute of Biotechnology，Shanxi University，Taiyuan 030006，China；2Agri-Biotechnology Research Center of Shanxi Province，Taiyuan 030031，Shanxi，China；3Shanxi Agricultural University，Taigu 030801，China |
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| Abstract: | Wheat, as an allohexaploid, is the most important cereal crop in the world. The origins of the three genomes have been a ‘hot spot’ for many geneticists and phylogeneticists since the famous Japanese geneticist Kihara suggested that wheat genome is composed of chromosomes of A, B and D genomes from three diploid progenitors. The studies on the origins of the three genomes have reported controversial results. Ribosomal DNA (rDNA) internal transcribed spacer (ITS) sequences are ubiquitous in most plants, they have been widely used in plant phylogenetics and systematics studies because of their unique characteristics compared with other types of DNAs. Specific primers were used to amplify the rDNA ITS sequences of common wheat (Triticum aestivum L.) by PCR. The amplified rDNA fragments were sequenced. Three types of ITS sequences were obtained. The results of cluster analysis by neighbor-joining method suggested that the sequence length of wheat ITS region was 602 bp, within which ITS1 and ITS2 had 8 and 20 variation sites, respectively. The range of genetic distances and genetic differentiation varied from 0 to 0.038, with the mean value of 0.021. The ITS sequences of common wheat resulted from this study were compared with those of its wild relatives, downloaded from GenBank, by MEGA, PAUP and PHYLIP programs, and the differentiation distances of ITS were calculated by Kimura-2 model program. A dendrogram was constructed with Bromus tectorum as the out-group. Based on the fact that common wheat had the ITS sequences highly similar to some of its wild relatives, we arrived at a conclusion that the formation of its genome is relatively recent events and the concerted evolution in its genome is incomplete, which provided the evidence at molecular level for that common wheat (Triticum aestivum L.) is an allohexaploid. By contrastive analysis to ITS sequences of common wheatandthe suspected donators of its genomes, we proposed that the most probable original donators of A, B, D genomes maybe T.urartu, T. speltoides, T. tauschii, respectively. We also proposed that the ‘concerted evolution’ is not concerted if we take various types of genes or DNA fragments into account. |
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| Keywords: | Wheat internal transcribed spacer（ITS) concerted evolution |
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