Total RNA was isolated by using Trizol (Invitrogen,USA). The quantity and integrity of RNA yield was as-sessed by using the Qubit®2.0 (Life Technologies, USA) and  Agilent 2200 TapeStation (Agilent Technologies, USA) separately. 1μg total RNA of each samples were used to prepare small RNA libraries by NEBNext® Multi- plex Small RNA Library Prep Set for Illumina (NEB,USA) according to manufacturer's instructions. The libraries were sequenced by HiSeq 2500 (Illumina,USA) with single-end 50bp at Ribobio Co. Ltd (Ribobio,China).