design: Raw reads were filtered via SOAPnuke (v1.4.0) by removing reads containing adaptors, poly-N or low quality, and then clean reads were obtained. Trinity (v2.0.6) was used to assemble the clean reads and Tgicl (v2.0.6) to perform clustering and eliminate redundant data in the assembled transcripts to obtain unique genes. The assembled transcripts were processed for further expression analysis and functional annotation.