library_construction_protocol: 1~3ug of total RNA was used for library construction by selecting index tags according to the instructions of VAHTS Universal V6 RNA-seq Library Prep Kit for Illumina  (NR604-01/02). The mRNA was enriched with magnetic beads with Oligo (dT), followed by fragmentation buffer to break the mRNA into short fragments, and a one-stranded cDNA was synthesized with  random hexamers primer using the mRNA as template, followed by buffer, dNTPs, RNase H and DNA The purified double-stranded cDNA is then end-repaired, A-tailed and sequenced, followed by fragment size selection, and finally PCR enrichment to obtain the final cDNA library.