Although the alteration of DNA methylation due to abiotic stresses, such as exposure to the toxic metal cadmium (Cd), has been often observed in plants, little is known about whether such epigenetic changes are linked to the ability of plants to adapt to stress. Herein, we report a close linkage between DNA methylation and the adaptational responses in Arabidopsis plants under Cd stress. Exposure to Cd significantly inhibited the expression of three DNA demethylase genes ROS1/DML2/DML3 (RDD) and elevated DNA methylation at the genome-wide level in Col-0 roots. Furthermore, the profile of DNA methylation in Cd-exposed Col-0 roots was similar to that in the roots of rdd triple mutants, which lack RDD, indicating that Cd-induced DNA methylation is associated with the inhibition of RDD. Interestingly, the elevation in DNA methylation in rdd conferred a higher tolerance against Cd stress and improved cellular Fe nutrition in the root tissues. In addition, lowering the Fe supply abolished improved Cd tolerance due to the lack of RDD in rdd. Together, these data suggest that the inhibition of RDD-mediated DNA demethylation in the roots by Cd would in turn enhance plant tolerance to Cd stress by improving Fe nutrition through a feedback mechanism.

中文翻译：

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抑制DNA脱甲基化可通过改善铁营养来增强植物对镉毒性的耐受性。

尽管经常在植物中观察到由于非生物胁迫（例如暴露于有毒金属镉（Cd））引起的DNA甲基化改变，但对于这种表观遗传变化是否与植物适应胁迫的能力有关的知之甚少。在本文中，我们报道了DNA甲基化与Cd胁迫下拟南芥植物的适应性反应之间的紧密联系。暴露于Cd会显着抑制三个DNA脱甲基酶基因ROS1 / DML2 / DML3（RDD）的表达，并在Col-0根的全基因组水平上抑制DNA甲基化。此外，Cd暴露的Col-0根中的DNA甲基化特征与rdd三元突变体的根相似，后者缺少RDD，表明Cd诱导的DNA甲基化与RDD的抑制有关。有趣的是，rdd中DNA甲基化的升高赋予了对Cd胁迫的更高耐受性，并改善了根部组织中的细胞铁营养。另外，由于rdd中RDD的缺乏，降低铁的供应量可以消除对Cd的耐受性。总之，这些数据表明，Cd抑制根系中RDD介导的DNA脱甲基将通过通过反馈机制改善铁的营养而反过来增强植物对Cd胁迫的耐受性。