RNA isolation for real-time quantitative PCR and microarray hybridisation
Total RNA from frozen tomato roots (150 mg) was extracted using TRI-Reagent (Sigma-Aldrich, St Louis, MO, USA). Contaminating genomic DNA was removed by 20 min incubation at 37ºC with 4 units of DNase I (Thermo Fisher Scientific, Waltham, MA, USA). After DNase I inactivation at 70ºC for 15 min, RNA was ethanol-precipitated and resuspended in 30 mL of diethylpyrocarbonate (DEPC)-treated water.