Six-d-old WT and #5 seedlings were collected and total RNA was extracted using Trizol reagent kit (Invitrogen) according to the manufacturer's instruction. The mRNA was enriched by using Oligo(dT) beads, fragmented, and cDNA was synthesized by using the NEBNext Ultra RNA Library Prep Kit for Illumina (NEB #7530, New England Biolabs). The purified double-strand cDNA fragments were end-repaired, A base added, and ligated to Illumina sequencing adapters. The ligation products were purified with the AMPure XP Beads (1.0X), subjected to size selection by agarose gel electrophoresis, and amplified by PCR. Sequencing was performed on an Illumina HiSeq 2500 platform performed by Gene Denovo Biotechnology Co.