library_construction_protocol: Total RNA of each sample was used to prepare the miRNA sequencing library, which included the following steps: 1) 3'-adapter ligation; 2) 5'-adapter ligation; 3) cDNA synthesis; 4) PCR amplification; 5) size selection of ~135-155 bp PCR amplified fragments (corresponding to ~15-35 nt small RNAs). The libraries were denatured as single-stranded DNA molecules, captured on Illumina flow cells, amplified in situ as clusters and finally sequenced for 36 cycles on Illumina HiSeq per the manufacturer's instructions.