design: Select total RNA >=1ug and use the NEBNext Ultra II RNA Library Prep Kit for Illumina (New England BiolabsInc; Ipswich, Massachusetts, USA (strand-specific library kit). NEBNext Ultra Directional RNA Library Prep Kit for Illumina), mRNAs with polyA tails were enriched by Oligo(dT) magnetic beads, and the mRNAs were subsequently randomly interrupted by ionic interruption using divalent cations. The fragmented mRNAs were used as templates, and random oligonucleotides were used as primers to synthesize cDNAs. cDNAs were purified from double-stranded cDNAs, followed by double-end repair and introduction of A bases at the 3' end, and ligated into sequencing junctions. The cDNA was screened for cDNAs of 400-500 bp using AMPure XP beads, amplified by PCR and the PCR products were purified again using AMPure XP beads to obtain the final library.