Liu Chang, Yang Xuejiao, Zhang Huakun, Wang Xutong, Zhang Zhibin, Bian Yao, Zhu Bo, Dong Yuzhu, Liu Bao
Key Laboratory of Molecular Epigenetics of the Ministry of Education (MOE), Northeast Normal University, Changchun, 130024, China.
Plant Mol Biol. 2015 May;88(1-2):53-64. doi: 10.1007/s11103-015-0307-0. Epub 2015 Mar 26.
The formation and evolution of common wheat (Triticum aestivum L., genome BBAADD) involves allopolyploidization events at two ploidy levels. Whether the two ploidy levels (tetraploidy and hexaploidy) have impacted the BBAA subgenomes differentially remains largely unknown. We have reported recently that extensive and distinct modifications of transcriptome expression occurred to the BBAA component of common wheat relative to the evolution of gene expression at the tetraploid level in Triticum turgidum. As a step further, here we analyzed the genetic and cytosine DNA methylation differences between an extracted tetraploid wheat (ETW) harboring genome BBAA that is highly similar to the BBAA subgenomes of common wheat, and a set of diverse T. turgidum collections, including both wild and cultivated genotypes. We found that while ETW had no significantly altered karyotype from T. turgidum, it diverged substantially from the later at both the nucleotide sequence level and in DNA methylation based on molecular marker assay of randomly sampled loci across the genome. In particular, ETW is globally less cytosine-methylated than T. turgidum, consistent with earlier observations of a generally higher transcriptome expression level in ETW than in T. turgidum. Together, our results suggest that genome evolution at the allohexaploid level has caused extensive genetic and DNA methylation modifications to the BBAA subgenomes of common wheat, which are distinctive from those accumulated at the tetraploid level in both wild and cultivated T. turgidum genotypes.
普通小麦（Triticum aestivum L.，基因组BBAADD）的形成和演化涉及两个倍性水平的异源多倍体化事件。这两个倍性水平（四倍体和六倍体）是否对BBAA亚基因组产生了不同影响，在很大程度上仍然未知。我们最近报道，相对于四倍体硬粒小麦（Triticum turgidum）基因表达的演化，普通小麦的BBAA组分发生了广泛而独特的转录组表达修饰。进一步地，在这里我们分析了一个提取的四倍体小麦（ETW）与一组不同的硬粒小麦群体（包括野生型和栽培型基因型）之间的遗传和胞嘧啶DNA甲基化差异，该四倍体小麦（ETW）具有与普通小麦的BBAA亚基因组高度相似的BBAA基因组。我们发现，虽然ETW的核型与硬粒小麦相比没有显著改变，但基于全基因组随机抽样位点的分子标记分析，它在核苷酸序列水平和DNA甲基化方面都与硬粒小麦有很大差异。特别是，ETW的全基因组胞嘧啶甲基化程度低于硬粒小麦，这与早期观察到的ETW转录组表达水平普遍高于硬粒小麦的结果一致。总之，我们的结果表明，异源六倍体水平的基因组演化对普通小麦的BBAA亚基因组造成了广泛的遗传和DNA甲基化修饰，这些修饰与野生型和栽培型硬粒小麦基因型在四倍体水平积累的修饰不同。
