A TMT-Based Proteomic Analysis of Osmoregulation in the Gills of Oreochromis mossambicus Exposed to Three Osmotic Stresses

Salinity and alkalinity are critical environmental factors that affect fish physiology and ability to survive. <i>Oreochromis mossambicus</i> is a euryhaline species that can endure a wide range of salinities and has the potential to serve as a valuable model animal for environmental science. In order to detect the histomorphological changes, antioxidant enzymes, and proteomic responses of <i>O. mossambicus</i> to different osmotic stresses, <i>O. mossambicus</i> was subjected to salinity stress (25 g/L, S_S), alkalinity stress (4 g/L, A_S), saline-alkalinity stress (salinity: 25 g/L, alkalinity: 4 g/L, SA_S), and freshwater (the control group; C_S). The histomorphological and antioxidant enzyme results indicated that salinity, alkalinity, and saline-alkalinity stresses have different degrees of damage and effects on the gills and liver of <i>O. mossambicus</i>. Compared with the control, 83, 187, and 177 differentially expressed proteins (DEPs) were identified in the salinity, alkalinity, and saline-alkalinity stresses, respectively. The obtained DEPs can be summarized into four categories: ion transport channels or proteins, energy synthesis and metabolism, immunity, and apoptosis. The KEGG enrichment results indicated that DNA replication and repair were significantly enriched in the salinity stress group. Lysosomes and oxidative phosphorylation were considerably enriched in the alkalinity stress group. Comparatively, the three most important enriched pathways in the saline-alkalinity stress group were Parkinson's disease, Alzheimer's disease, and Huntington's disease. The findings of this investigation yield robust empirical evidence elucidating osmoregulatory mechanisms and adaptive biological responses in euryhaline teleost, thereby establishing a scientific foundation for the cultivation and genomic exploration of high-salinity-tolerant teleost species. This advancement facilitates the sustainable exploitation of saline-alkaline aquatic ecosystems while contributing to the optimization of piscicultural practices in hypersaline environments.