Genetic Mechanism for Antioxidant Activity of Endogenous Enzymes under Salinity and Temperature Stress in Turbot (Scophthalmus maximus)

Three antioxidant properties (corresponding to the enzymes superoxide dismutase (SOD), catalase, and glutathione peroxidase) were measured in the livers of Scophthalmus maximus under different salinities/temperatures (5, 10, 20, 30, and 40‰/17, 20, 23, 25, and 28 °C). Split-plot (SP) analysis, additive main effects, and multiplicative interaction (AMMI) and genotype × environment interaction (GGE) biplots were used to analyze genotype × salinity/temperature interactions for antioxidant properties. The results of the SP analysis show that the activity of the three antioxidant properties was significantly (p < 0.01) affected by salinity/temperature, antioxidant, and salinity/temperature × antioxidant interaction. The results of the AMMI analysis for salinity reveal that the effect of genotype, salinity, and genotype × salinity interaction on antioxidant properties reached a significant level (p < 0.001); 92.1065%, 2.6256%, and 4.4360% of the total sum of squares for antioxidant property activity were attributable to the effects of genotype, salinity, and genotype × salinity interaction, respectively. The results of GGE biplot analysis for salinity reveal differences in the activity ranking of the three antioxidant properties under five salinities; this difference expands with an decrease or increase in salinity from 30‰ (optimum salinity). A salinity of 5‰ had the strongest ability to identify the three antioxidant properties. The five experimental salinities were divided into one region, and SOD activity was the highest in this region. In a comprehensive analysis of stability and activity, SOD had the best activity and stability. The results of AMMI analysis for temperature reveal that genotype, temperature, and genotype × temperature interaction had significant effects on the antioxidant properties (p < 0.001); 82.4720%, 4.0666%, and 12.0968% of the total sum of squares for antioxidant property activity were attributable to the effects of genotype, temperature, and genotype × temperature interaction, respectively. The results of GGE biplot analysis for temperature reveal a large difference in the activity ranking of antioxidant properties between 17 °C and the other four temperatures, while only small differences in the activity rankings were detected among the other four temperatures. The difference in the activity ranking of antioxidant properties was greatest between the temperatures of 17 and 20 °C. A temperature of 17 °C showed the strongest ability to distinguish the three antioxidant properties. Additionally, the five test temperatures were grouped into one region, and comprehensive analysis of activity and stability showed that SOD had the best activity and stability.