All wild‐type and mutant plants were in the Arabidopsis thaliana accession Columbia (Col‐0) background. The h1.1‐1 (SALK_128430C) and h1.2‐2 (GK‐116E08) plant lines were described previously (Rutowicz et al., 2015 ); h1.1‐1 h1.2‐2 double mutants were generated by crossing (H1, histone 1). The cmt2‐5 (SAIL_906_G03) and cmt3‐11 (SALK_148381) mutants were described previously (Chan et al., 2006 ; Shen et al., 2014 ) (CMT, CHROMOMETHYLASE 2).
Plants were grown on plates with 1/2 Murashige & Skoog medium including vitamins (Duchefa, Haarlem, The Netherlands) and 1% sucrose. Zebularine‐treated plants were grown on ½MS medium supplemented with 40 µM Zebularine (Abcam, Cambridge, UK). Plates were sealed with micropore tape and stratified for 2 d at 4°C in the dark. The plates were then transferred to a growth chamber with a 16 h : 8 h, light (110 µmol m−2 s−1, 22°C) : dark (20°C) photoperiod. Ten‐day‐old seedlings were used for RNA extraction. For heat stress treatments, we incubated 10‐d‐old seedlings at 4°C for 1 h followed by 37°C for 24 h in the dark, as published previously (Shen et al.,2014 ). The survival rate of heat‐treated plants was determined by incubating 10‐d‐old seedlings in the dark at 4°C for 1 h followed by 37°C for 36 h and then removing to normal conditions for 2 d. Seedlings were defined as lethal if they showed bleaching of shoot apices and leaves.
Plants were grown on plates with 1/2 Murashige & Skoog medium including vitamins (Duchefa, Haarlem, The Netherlands) and 1% sucrose. Zebularine‐treated plants were grown on ½MS medium supplemented with 40 µM Zebularine (Abcam, Cambridge, UK). Plates were sealed with micropore tape and stratified for 2 d at 4°C in the dark. The plates were then transferred to a growth chamber with a 16 h : 8 h, light (110 µmol m−2 s−1, 22°C) : dark (20°C) photoperiod. Ten‐day‐old seedlings were used for RNA extraction. For heat stress treatments, we incubated 10‐d‐old seedlings at 4°C for 1 h followed by 37°C for 24 h in the dark, as published previously (Shen et al.,