镉胁迫下二倍体和同源四倍体油菜DNA甲基化差异分析

二倍体与四倍体在逆境抗性上的差别可以从表观遗传学的角度予以解释。本研究以“矮脚黄”纯合二倍体和同源四倍体油菜为材料，采用DNA甲基化敏感扩增多态性分析（Methylation-sensitive amplification polymorphism，MSAP）方法和HDA-GT12TM全自动凝胶毛细管核酸电泳检测技术，在全基因组水平上研究了CdCl2胁迫下油菜二倍体和四倍体DNA序列中CCGG位点的甲基化水平及模式变化特征差异。采用56对引物在4个处理样品中共检测出9 687个基因位点。结果显示，二倍体和四倍体在镉胁迫下，其总甲基化水平、全甲基化水平和半甲基化水平较各自的对照均有一定程度的上升。由此可见，镉胁迫导致四倍体和二倍体甲基化水平的提高，但四倍体基因组在镉胁迫下拥有更高的DNA甲基化水平。DNA甲基化模式分析表明，镉胁迫导致二倍体和四倍体的过甲基化位点数均高于去甲基化位点数，二者在镉胁迫下去甲基化位点数差异不大，但四倍体发生过甲基化的位点数要明显多于二倍体。

COMPARISON BETWEEN TETRAPLOID TURNIP (Brassica rapa) AND ITS DIPLOID PROGENITOR OF DNA METHYLATION UNDER CADMIUM STRESS

The difference of stress tolerance between diploids and tetraploids may be explained from the view of epigenetics. In this study, an autotetraploid turnip (cv. Ai-Jiao-Huang 4X) and its diploid progenitor (cv. Ai-Jiao-Huang 2X) under cadmium stress were compared for their degree of genomic DNA methylation and the pattern of DNA methylation at CCGG sites by MSAP (methylation-sensitive amplification polymorphism) and the high-speed HDA-GT12 (TM) analysis system. A total of 56 pairs of selective primers which generated 9687 genetic loci were applied. Compared to the respective control, the diploid and tetraploid under cadmium stress had a higher ratio of general methylation, full methylation and half methylation, indicating that, cadmium stress gave rise to an increase of DNA methylation degree for both the diploid and tetraploid type. Nevertheless, the DNA methylation of the tetraploid correlated more closely to cadmium stress than that of the diploid did. Analysis of DNA methylation patterns suggested that the number of hypermethylation sites was greater than those of demethylation sites both in the diploid and tetraploid under cadmium stress. There was no significant difference between diploid and tetraploid for the number of demethylation sites, however, the tetraploid had a higher number of hypermethylation sites.