Transcriptome Reveals the Mechanism of Immunity in the Low Salinity Stress of the Chinese Shrimp (Fenneropenaeus chinensis)

The Chinese shrimp (Fenneropenaeus chinensis) is mainly economically important cultured species in the aquaculture of China, and it has a strong adaptability to changes in salinity (18ppt-32ppt). To have a better understanding of the underlying molecular mechanism of low salinity in Chinese shrimp, Illumina sequencing technology were performed for a transcriptome analysis in the hepatopancreas of Chinese shrimp which were treated in low salinity stress group (5ppt) and normal salinity group (20ppt) respectively. Totally, we obtained 426,456 unigenes with an average length of 482.38 bp. Then 2,769 differently expression genes (DEGs) were identified by a comparative transcriptome analysis, of which 1,690 DEGs showed up-regulated and 1,079 DEGs showed down-regulated. More reactive oxygen species(ROS) would be accumulated when Chinese shrimp were challenged with low salinity stress, then numerous signaling pathways played a significant role in signal transduction, such as Toll signaling pathway, Wnt signaling pathway. Meanwhile, glutathione peroxidase 3 (GPX3), mpv17-like protein (MPV17L), glutathione S-transferase (GST), catalase (CAT), thioredoxin (Trx) were up-regulated to defense the low salinity stress which were involved in the antioxidant system. If the antioxidant system failed to deal with low salinity stress, cell structure and function would be damaged and apoptosis would be activated. The genes associated with heat shock protein (heat shock protein 60, heat shock protein 90, heat shock protein 21, heat shock protein 22, heat shock protein 27) were also up-regulated. Seven genes involved in low salinity response were discovered and validated by real-time quantitative PCR. In conclusion, our study provides valuable information on the low salinity adaption mechanism of Chinese shrimp. And the sequence of transcripts reported in this paper was comprehensive, which can provide a rich source for the identification of novel genes in other shrimps with low salinity.