library_construction_protocol: TRIzol reagent (Invitrogen, USA) was used to extract total RNA from cells. Enrichment of mRNA with polyA structure in total RNA by Oligo(dT) magnetic beads. The RNA was broken to a length of about 300bp by means of ion interruption. Synthesize cDNA with 6-base random primers and reverse transcriptase.The first strand of cDNA was synthesized using RNA as template, and the second strand of cDNA was synthesized using the first strand of cDNA as the template.