Non-CG DNA Methylation Regulates Root Stem Cell Niche Maintenance, Auxin Signaling, and ROS Homeostasis in <i>Arabidopsis</i> Under Cadmium Stress
Emanuela Talarico | Eleonora Greco | Fabrizio Araniti | Adriana Chiappetta | Leonardo Bruno
Non-CG DNA methylation plays a critical role in regulating root development and stress responses in <i>Arabidopsis thaliana</i> under cadmium (Cd<sup>2+</sup>) exposure. We compared wild type (WT) plants with the <i>ddc</i> triple mutant (deficient in <i>DRM1</i>, <i>DRM2</i>, and <i>CMT3</i>) to assess how epigenetic modifications affect the root apical meristem (RAM) under 100 µM and 150 µM CdCl<sub>2</sub> treatments. Cd<sup>2+</sup> exposure led to RAM disorganization, reduced cortical cell number, and quiescent center (QC) cell loss in WT roots, while <i>ddc</i> mutants maintained meristem integrity and exhibited QC cell expansion. Auxin signaling, assessed via <i>pDR5::GFP</i>, was disrupted in WT roots at high Cd<sup>2+</sup> levels but remained stable in <i>ddc</i> mutants. Similarly, WT roots showed elevated reactive oxygen species accumulation under stress, whereas <i>ddc</i> mutants displayed a reduced oxidative response. These results suggest that non-CG DNA methylation suppresses key regulators of stem cell maintenance, hormonal balance, and redox homeostasis during heavy metal stress. Loss of this methylation in the <i>ddc</i> mutant confers enhanced resilience to Cd<sup>2+</sup> toxicity, highlighting an epigenetic mechanism underlying root stress adaptation.
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