Integrated miRNA and mRNA analysis in gills of spotted sea bass reveals novel insights into the molecular regulatory mechanism of salinity acclimation

As a prominent abiotic factor, salinity affects fish growth, development, reproduction, and physiological activities severely. In the present study, we performed histological observations and miRNA-mRNA integrated transcriptomic analysis in the gill of spotted sea bass (Lateolabrax maculatus) under different salinity conditions. Histological investigation showed that the morphological indices (filament thickness, lamella thickness, lamella height, distance between lamella, lamella basal length) and the number of red blood and mucous cells were significantly different between FW and SW gills. A total of 1022 differentially expressed genes (DEGs) and 42 differentially expressed miRNAs (DEmiRs) have been identified among different salinity groups, generating 224 predicted miRNA-mRNA pairs that potentially associated with salinity acclimation. Protein-Protein Interaction networks revealed that 5 (fbp1b, fbp2, gapdh, prkag2a and prkag3b) and 7 (zbtb16a, e2f5, brd4, brd3a, mef2ca, ncor1 and ezh2) hub genes may play important functions during FW and SW adaption, respectively. Notably, functional enrichment analysis suggested that DEGs and DEmiRs involved in glucose metabolism, signal transduction pathways, as well as hematopoiesis and vascular function maintaining associated molecules may be essential for osmoregulation in gills. Our findings will not only lay the basis for understanding the molecular mechanisms of salinity acclimation in euryhaline fishes, but also provide a list of molecular markers that can be used for improving fish salinity tolerance capabilities, and artificial breeding of salinity-tolerance strains for stenohaline species.