design: The transcriptome library was prepared using RNA Sample Prep Kit. mRNA was isolated by oligo(dT) beads and then fragmented. After that, double-stranded cDNA was synthesized using a SuperScript double-stranded cDNA synthesis kit (Invitrogen) with random hexamer primers (Illumina). The synthesized cDNA was subjected to end-repair, phosphorylation and A base addition according to Illuminas library construction protocol.