Non-denaturing agarose gel (1.5%) electrophoresis in TBE with in-gel ethidium bromide staining of RNA isolated from Arabidopsis, wheat and tomato leaves using TRI reagent (SIGMA) (labelled as 1) or the protocol by Oñate-Sánchez and Vicente-Carbajosa  (labelled as 2). In all cases, 500 theoretical nanograms, according to the spectrophotometric quantification, were loaded per lane. Samples were extracted and analysed in triplicates. Starting material per sample was as follows: Arabidopsis – eight leaf discs (7 mm diameter) of five-week-old plants grown in short day conditions; wheat – eight leaf discs (7 mm diameter) of four-week-old plants grown in the glasshouse; tomato – eight leaf discs (7 mm diameter) of five-week-old plants grown in the glasshouse. Samples were resuspended in 30 μL of water in all cases. The RNA ladder is the 0.5-10 Kb RNA ladder (Life Technologies).