design: RNA sequences for each sample were first reversed transcribed into cDNA following the Smart-seq2 protocol (Picelli et al., 2014),which was then randomly fragmented with Tn5 enzymes and linked with sequencing adapters to obtain a complete cDNA library for each individual sample. Primers were then added to the cDNA libraries for PCR amplification, and fragments ranging between 150 to 350 bp were selected for further cDNA circularization to construct sequencing libraries. The samples were then sequenced on a BGISEQ-500 platform using a 100nt paired-end sequencing protocol.