Abstract
DNA methylation plays an important role in modulating plant growth plasticity in response to stress, but mechanisms involved in such control need further investigation. We used drm1 drm2 cmt3 mutant of Arabidopsis thaliana, defective in DNA methylation, to explore metabolic pathways downstream epigenetic modulation under cadmium (Cd) stress. To this aim, a transcriptomic analysis was performed on ddc and WT plants exposed to a long-lasting (21 d) Cd treatment (25/50 µM), focusing on hormone genetic pathways. Growth parameters and hormones amount were also estimated. Transcriptomic data and hormone quantification showed that, under prolonged Cd treatment, level and signalling of growth-sustaining hormones (auxins, CKs, GAs) were enhanced and/or maintained, while a decrease was detected for stress-related hormones (JA, ABA, SA), likely as a strategy to avoid the side effects of their long-lasting activation. Such picture was more effective in ddc than WT, already at 25 µM Cd, in line with its better growth performance. A tight relationship between methylation status and the modulation of hormone genetic pathways under Cd stress was assessed. We propose that the higher genome plasticity conferred to ddc by DNA hypomethylated status underlies its prompt response to modulate hormones genetic pathways and activity and assure a flexible growth.
Highlights
Plants, as sessile organisms, are under constant influence of environment, which modulates their growth and development through a multiplicity of signals
At 21 d after germination (DAG) root of Cdtreated samples was longer in ddc vs wild type (WT), at the lowest Cd concentration
Control plants of both ddc and WT exhibited a complete leaf series, most leaves resulted smaller in ddc (Fig. 1B,C)
Summary
As sessile organisms, are under constant influence of environment, which modulates their growth and development through a multiplicity of signals. A role in such plasticity is paid by epigenetic mechanisms, including DNA methylation, which act on the chromatin status allowing a simultaneous and wide regulation of gene expression. Studies on both the model Arabidopsis thaliana and fruit crops demonstrated that methylome dynamic, beside playing a role at evolution level, is involved in the control of plant ontogenesis and modulate plant response to external cues, including multiple s tresses[2]. Either hypermethylation or hypomethylation were detected in plants under different stressors[3] Despite all this information, many aspects of the mechanisms that translate the information superimposed by DNA methylation into downstream regulation of gene expression remain still unclear. Cd in the soil is adsorbed by plants and at high concentration inhibits their growth and development by impacting on several metabolic processes through a wide range of structural and molecular changes, including epigenetic m odifications[9]
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