RNA extraction and quantification
Total RNA from shoots and roots of Arabidopsis was isolated with TRI Reagent (Ambion), cleaned using in-column DNAse treatment with the RNeasy Mini Kit (Qiagen) (Montero-Palmero, Martín-Barranco, Escobar, & Hernández, 2013), and quantified n a NanoDrop ND-1000 spectrophotometer (Thecnologies Inc.). RNA integrity was determined with an Agilent 2100 Bioanalyzer equipped with an RNA 6000 Nano LabChip Kit (Agilent Technologies, Santa Clara, CA, USA) using the RNA integrity number (RIN) algorithm of three independent biological replicates (Schroeder et al., 2006), which showed satisfactory RNA quality in all samples, particularly in those prepared from Hg-treated plants (Supplementary Fig. 2).