Comparative transcriptome analysis of juvenile greater amberjack (Seriola dumerili) revealed the molecular responses of the kidney to chronic salinity stress

Salinity is an important environmental factor, and fluctuations in saline-alkali levels that exceed the osmoregulatory capacity of fish may have profound effects on various physiological functions of teleosts. The greater amberjack is highly valued commercially owing to its rapid growth and excellent meat quality. In this study, the juvenile greater amberjack were reared for 30 days under optimal salinity (30 ppt) as well as hypo- (20 ppt) and hyper-salinity (40 ppt) conditions. Histologically, the structure of the kidney was damaged under chronic salinity stress, characterized by hypertrophy at the edges of the columnar epithelial cells in the renal tubules, while the central side was tightened. Through comparative transcriptome analysis of the kidney, a total of 1103, 51, and 1711 differentially expressed genes (DEGs) were identified in the K20 vs. K30 (686 up- and 417 down-regulated), K40 vs. K30 (14 up- and 37 down-regulated), and K20 vs. K40 (1170 up- and 541 down-regulated) salinity stress groups, respectively. Certain DEGs enriched in the cell cytoskeleton (LOC111217621, tubb5, and LOC111234965) and cell apoptosis (tnfrsfa, LOC111218420, LOC111223891, LOC111223286, and bcl2) were identified by kidney transcriptome analysis in response to salinity stress. Furthermore, DEGs associated with lipid and carbohydrate metabolism (elovl6l, acsl4, msmo1, pck1, g6pc1, pfkfb3, and ldha), ion transport (kcnk5, slc4a4, slc9a3, slc41a1, and slc22a2), and immune response (nfkbiaa, nfkbia, and LOC111231462) were identified. These findings suggest that the cytoskeleton was damaged, along with variations in ion transport, lipid and carbohydrate metabolism, and immune responses to salinity stress. The current findings enhance our understanding of the physiological responses of greater amberjack to salinity stress, which could be beneficial in developing strategies to optimize the aquaculture and artificial breeding of this species in environments characterized by fluctuating salinity patterns.