The interplay between Ca2+and ROS in regulating (3-carotene biosynthesis in Dunaliella salina under high temperature stress

Temperature influences biomass and (3-carotene production in Dunaliella salina, while high temperature generally induces (3-carotene biosynthesis via increased ROS, the intricate and incomplete mechanisms necessitate the identification of novel regulators and their interactions with ROS. A comprehensive analysis of physiological responses to different temperatures was investigated in this study, including cell proliferation, biomass growth, carbon utilization efficiency, (3-carotene synthesis, chlorophyll profiles, photosynthetic efficiency, ROS, antioxidant content, activity of antioxidant enzymes, free radical scavenger capacity, and Ca2+ level. The results showed that 34 degrees C is the optimal temperature for (3-carotene accumulation, and high temperature impairs chlorophyll, photosynthesis, and carbon utilization by enhancing oxidative stress. High temperature (40 degrees C vs 25 degrees C) triggers a simultaneous increase in ROS (24.34-fold) and Ca2+ levels (16.04-fold), implicating Ca2+ as a temperature-sensitive regulator of (3-carotene that potentially interacts with ROS. Further chemical treatments at 34 degrees C demonstrated that Ca2+ supplementation enhanced biomass and increased (3-carotene yield and content by 4.81 %, 11.79 %, and 19.99 %, respectively. Supplementation with H2O2 increased the yield and content of (3-carotene (5.62 % and 30.57 %) but reduced biomass (19.23 %). Notably, supplemented H2O2 decreased cellular Ca2+, while supplemented Ca2+ enhanced antioxidant capacity. This study identifies Ca2+ as a novel regulator of high-temperature (3-carotene biosynthesis and shows its interplay with ROS.