Seed germination at 12h
Total RNA was extracted from germinating seeds at 12h after imbibition using TRIZOL reagent (TianGen, China) according to the manufacturer’s instructions. Small RNAs of 18~30nt were purified from the total RNA by 15% polyacrylamide gel electrophoresis (PAGE). A pair of Solexa adaptors was ligated to the 5’ and 3’ termini of the small RNAs, then reverse transcription was performed by Super-Script II Reverse Transcriptase (Invitrogen) and amplified using 15 PCR cycles to produce sequencing library.