Transcriptome of hepatopancreas in kuruma shrimp Marsupenaeus japonicus under low-salinity stress

The kuruma shrimp Marsupenaeus japonicus is one of the most commercially important shrimp species in the world. Low salinity would affect the penetration and immunity, and even led to its death of the shrimp. However, little is known about the molecular mechanism of the effect. Therefore, hepatopancreas of M. japonicus reared under low-salinity stress for 6, 12, 24, 48, and 96 h was analyzed and the results were compared with that of the control group using transcriptomics. After removing reads containing adapters, 88 890 960-1 051 300 444 clean reads were generated from 10 libraries in the control group and experimental group. Compared with the control group, 811, 589, 1 095, 745, and 875 differentially expressed genes were obtained in the five treatment groups. The N50 and N90 lengths of the transcripts were 1 746 bp and 436 bp, respectively. The top 20 gene ontology terms and Kyoto Encyclopedia of Genes and Genomes pathways associated with the differentially expressed genes were related mainly to osmotic regulation (ion exchange, lipid metabolism and carbohydrate metabolism), immune regulation (cellular and humoral immunity), chitin metabolism, and related functions. The differential expression patterns of nine randomly selected genes were confirmed by quantitative real-time PCR. This is the first report of osmotic regulation-related genes that are differentially expressed under low-salinity stress in the hepatopancreas of M. japonicus. Furthermore, we found that M. japonicus initiated its own immune regulation under low-salinity stress. These results will help elucidating the mechanism of osmotic regulation and immune responses in this shrimp species.