^(60)Co-γ射线诱导的小麦基因组DNA的甲基化变异

The Variation of DNA Cytosine Methylation in Wheat Genome Induced by^(60)Co-γ Rays

诱发突变技术在小麦品种改良中具有重要作用,辐射诱变能通过改变DNA甲基化的方式而影响基因组稳定性。本研究分别采用100和150Gy60Co-γ射线处理小麦品种京411(J411)干种子,利用甲基化敏感扩增多态性技术检测处理后幼根和幼叶基因组甲基化相对水平的变化及甲基化模式的变异规律。结果表明,γ射线处理对幼苗的苗高和根长都有显著抑制作用。与未处理对照比较,处理后小麦幼苗叶片和根部DNA胞嘧啶甲基化相对水平均发生变化,叶片的甲基化相对水平下降,而根中升高。2种处理剂量下,叶片和根的甲基化模式变异均表现为CG位点变化率高于CNG位点变化率。不同位点的甲基化模式变异在诱变后也存在一定的差异。叶片中不同剂量下CG位点和CNG位点的去甲基化率都高于相应位点的甲基化率;根部CNG位点在所有剂量下的去甲基化率都低于相应位点的甲基化率,而CG位点在100Gy剂量下去甲基化率高于相应位点的甲基化率,而在150Gy剂量下的去甲基化率则低于相应位点的甲基化率,反映出同一组织同一位点在不同诱变剂量处理下甲基化模式变异存在一定的差异。

Mutation technique has played an important role in wheat improvement. Nuclear irradiation may affect genome stability by altering DNA methylation patterns（ including hyper-methylation and hypo-methylation）. In this study,seeds of wheat variety Jing 411 were irradiated by60Co-γ rays with the dose of 100 Gy and 150 Gy,respectively. Variation of DNA cytosine methylation in seedling leaf and root were detected by methylation sensitive amplification polymorphism（ MSAP）. The results showed that seedling height and root length were significantly inhibited after60Co-γ ray irradiation. DNA cytosine methylation in leaves and roots was altered after60Co-γ ray treatment. Compared with the control,the methylation variations in leaves and roots were different. The relative level of methylation in leaves was decreased,but increased in roots,indicating tissue specificity. The rates of demethylation variation in leaves at both dosages were higher than those of methylation,and it was opposite in roots. At different sites,the variations of methylation patterns were different. At CG and CNG sites of leaves,demethylation rates were higher than those of methylation at both dosages. In root,demethylated variation rate of CNG sites were lower than the corresponding methylation sites. Under 100 Gy,the demethylation variation rate at CG sites is higher than the methylation variation rate of the corresponding sites, and it is consistent with methylation patterns variation of leaves. under 150 Gy, the methylation variation rate at CG sites is higher than the demethylation variation rate of the corresponding sites. The result indicated that the variation of methylation pattern,induced by different dosage of60Co-γ rays,even in the same organization and same site was different.