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Total RNA was extracted by TRIzol (Invitrogen Life Technologies, Carlsbad, CA, USA), and concentrations and purity were measured using NanoDrop (NanoDrop Technologies, Wilmington, DE, USA). An RNA Nano 6000 Assay Kit was used to assess integrity (Agilent Technologies, CA, USA). Here, 1000 ng RNA per sample was used as the input material for the cDNA library construction. Sequencing libraries were generated by the NEBNextUltraTM RNA Library Prep Kit for Illumina (NEB, USA), per the manufacturers instructions. To select cDNA fragments that were preferentially 240 bp in length, the library fragments were purified with the AMPure XP system (Beckman Coulter, Beverly, USA) and then amplified by PCR. Finally, PCR products were purified (AMPure XP system), and library quality was assessed using the Agilent Bioanalyzer 2112 system. The library preparations were sequenced on an Illumina platform, and paired-end reads were generated.