Effects of reactive oxygen species on α-tocopherol production in mitochondria and chloroplasts of Euglena gracilis

Abstract

The effects of reactive oxygen species (ROS) on α-tocopherol production in mitochondria and chloroplasts of Euglena gracilis were investigated. Addition of an organic carbon source to the medium resulted in increased mitochondrial activity, intracellular O2 - concentration and α-tocopherol productivity in E. gracilis W14ZUL (a chloroplast deficient mutant). α-Tocopherol productivity of the wild-type strain (with both mitochondria and chloroplast) was higher than that of the W14ZUL strain. In the case of the wild strain, the O2 − generated in chloroplasts was efficiently scavenged by the α-tocopherol synthesized inside the chloroplast. In photoheterotrophic culture (with an organic carbon source), there was a positive correlation between α-tocopherol production and O2 − generation. Addition of 3-(3,4-dichlorophenyl)-1,1-dimethylurea (an inhibitor of photosynthesis) resulted in increased O2 − generation and α-tocopherol productivity. These results indicate that the ROS generated in mitochondria and chloroplasts play important roles in α-tocopherol production by E. gracilis. The presence of chloroplasts and generation of intracellular ROS are important for efficient production of α-tocopherol.