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

Abstract

Temperature influences biomass and β-carotene production in Dunaliella salina, while high temperature generally induces β-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, β-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 °C is the optimal temperature for β-carotene accumulation, and high temperature impairs chlorophyll, photosynthesis, and carbon utilization by enhancing oxidative stress. High temperature (40 °C vs 25 °C) triggers a simultaneous increase in ROS (24.34-fold) and Ca²⁺ levels (16.04-fold), implicating Ca²⁺ as a temperature-sensitive regulator of β-carotene that potentially interacts with ROS. Further chemical treatments at 34 °C demonstrated that Ca²⁺ supplementation enhanced biomass and increased β-carotene yield and content by 4.81 %, 11.79 %, and 19.99 %, respectively. Supplementation with H₂O₂ increased the yield and content of β-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 β-carotene biosynthesis and shows its interplay with ROS.