Total RNA was isolated from seedlings with the TRIzol reagent procedure of Invitrogen, then poly(A)+ RNA was purified with Qiagen oligotex. One microgram poly(A)+ RNA was converted into ds-cDNA using T7-oligo(dT) primers. Biotin-labeled cRNA was generated by in vitro transcription reactions using ENZO labeling kit, fragmented and then 20 micrograms of fragmented cRNA were hybridized to the arrays according to Affymetrix instructions.