Salinity Stress Mechanisms in Sepia esculenta Larvae Revealed by Integrated Biochemical and Transcriptome Analyses

The stable marine environment is conducive to the development of the aquaculture industry. However, with the change of seawater salinity in recent years, it has had a great impact on the survival and breeding of cephalopods such as Sepia esculenta. In this study, biochemical measurement and transcriptome sequencing were performed on the larvae of S. esculenta after different salinity stresses (salinity of 20 ppt and 40 ppt), and the reliability of transcriptome results was proved by physiological indexes. We performed Gene Ontology (GO), Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis, and gene set enrichment analysis (GSEA) on all annotated genes, and gene sets were identified, including chemokine signaling pathways, MAPK signaling pathways, and cell cycle pathways. Finally, we constructed the protein-protein interaction networks (PPI) between the core genes in these gene sets and differentially expressed genes (DEGs) to identify key genes, including NFKBIA. Among them, the NFKBIA is not only a core gene in the chemokine signaling pathway gene set under four stresses but also has a high number of protein interactions. We speculate that this gene may have important immunomodulatory functions in the face of different time and salinity stresses. The results of our study explored the molecular mechanism of S. esculenta in the face of environmental stress, revealed the key molecular regulatory pathways for its survival and adaptation under complex environmental pressures, and may provide insights relevant to the development of S. esculenta pond culture.