Transcriptomic and metabolomic analysis of the main stress-related pathways in the DNA methylation-defective ddc mutant of Arabidopsis thaliana exposed to cadmium

Plant growth and development strongly depend on environmental conditions and can be frequently hindered by several abiotic and biotic stress factors. To counteract these factors plants evolved complex defence strategies, including epigenetic modifications, to appropriately regulate gene expression. This study extends our previous investigations on the role of DNA methylation in cadmium (Cd) stress tolerance using the Arabidopsis thaliana drm1 drm2 cmt3 (ddc) mutant, defective in both de novo and maintenance DNA methylation. It is known that Cd toxicity is related to oxidative stress induction and cellular homeostasis disruption, impairing growth and metabolism. Through transcriptomic analysis we investigated Cd-induced modulation of genetic pathways (GPs) specifically related to defence mechanisms against metal-toxicity, such as antioxidant and detoxification pathways and mitogen-activated protein kinase (MAPK) signalling. To understand the whole metabolic shift under Cd stress, targeted metabolomic analysis was also performed. A global genotype-specific downregulation of analysed GPs and metabolic profiles was detected in both ddc and wild type plants, in line with Cd detrimental but differential effects on their growth. By integrating the present and our previous findings we discuss the important role of epigenetic regulation in modulating Cd stress adaptation.