Study on the osmotic response and function of -inositol oxygenase in euryhaline fish nile tilapia ().

To understand the role of -inositol oxygenase () in the osmotic regulation of Nile tilapia, its expression was analyzed in various tissues. The results showed that the expression of gene was highest in the kidney, followed by the liver, and was significantly upregulated in the kidney and liver under 1 h hyperosmotic stress. The relative luminescence efficiency of the gene transcription starting site (-4,617 to +312 bp) under hyperosmotic stress was measured. Two fragments (-1,640/-1,619 and -620/-599) could induce the luminescence activity. Moreover, the -1,640/-1,619 and -620/-599 responded to hyperosmotic stress and high-glucose stimulation by base mutation, suggesting that osmotic and carbohydrate response elements may exist in this region. Finally, the salinity tolerance of Nile tilapia was significantly reduced after the knocking down of gene. The accumulation of -inositol was affected, and the expression of enzymes in glucose metabolism was significantly reduced after the gene was knocked down. Furthermore, hyperosmotic stress can cause oxidative stress, and MIOX may help maintain the cell redox balance under hyperosmotic stress. In summary, MIOX is essential in osmotic regulation to enhance the salinity tolerance of Nile tilapia by affecting -inositol accumulation, glucose metabolism, and antioxidant performance. -inositol oxygenase (MIOX) is the rate-limiting enzyme that catalyzes the first step of MI metabolism and determines MI content in aquatic animals. To understand the role of in the osmotic regulation of Nile tilapia, we analyzed its expression in different tissues and its function under hyperosmotic stress. This study showed that is essential in osmotic regulation to enhance the salinity tolerance of Nile tilapia by affecting -inositol accumulation, glucose metabolism, and antioxidant performance.