Differential gene expression in the intestine of sea cucumber (Apostichopus japonicus) under low and high salinity conditions

Sea cucumber, Apostichopus japonicus is an important species for aquaculture, and its behavior and physiology can change in response to changing salinity conditions. For this reason, it is important to understand the molecular responses of A. japonicus when exposed to ambient changes in salinity. In this study, RNA-Seq provided a general overview of the gene expression profiles in the intestine of A. japonicus exposed to high salinity (SD40), normal salinity (SD30) and low salinity (SD20) environments. Screening for differentially expressed genes (DEGs) using the NOISeq method identified 109, 100, and 89 DEGs based on a fold change of ≥ 2 and divergence probability ≥ 0.8 according to the comparisons of SD20 vs. SD30, SD20 vs.SD40, and SD30 vs. SD40, respectively. Gene ontology analysis showed that the terms “metabolic process” and “catalytic activity” comprised the most enriched DEGs. These fell into the categories of “biological process” and “molecular function”. While “cell” and “cell part” had the most enriched DEGs in the category of “cellular component”. With these DEGs mapping to 2119, 159, and 160 pathways in the Kyoto Encyclopedia of Genes and Genomes database. Of these 51, 2, and 57 pathways were significantly enriched, respectively. The osmosis-specific DEGs identified in this study of A. japonicus will be important targets for further studies to understand the biochemical mechanisms involved with the adaption of sea cucumbers to changes in salinity.