design: The RNA was extracted using Trizol reagent. After quality inspection of RNA, the RNA was enriched with Oligo (dT) beads, then fragment buffer was added to the obtained RNA to make the RNA into short fragments. The fragments were used as templates to synthesize the first-strand cDNA with six base random primers. The second-strand cDNA was synthesized and purified using the QIAQuick PCR kit (QIAGEN, Hilden, Germany). The obtained cDNA was subjected to end repair, dA tailing, and adaptor ligation, and then recovered by agarose gel electrophoresis. The resulting fragment was amplified by PCR. Finally, the cDNA libraries were sequenced using Illumina HiSeq4000 platform (Illumina Inc., San Diego, USA) at LC Sciences Co., Ltd at Hangzhou, China