Characterization of chloroplastic/mitochondrial (cp/mt) MDAR knockout line of Arabidopsis thaliana.

Abstract

Ascorbate (AsA) functions as an antioxidant to scavenge reactive oxygen species (ROS). Monodehydroascorbate reductase (MDAR) catalyzes the regeneration of AsA from its primary oxidant monodehydroascorbate. One of five MDAR genes in the Arabidopsis genome encodes the region of the transit peptide for dual targeting to mitochondria and chloroplasts. Because mitochondria and chloroplasts are the main sites of the generation of ROS in plant cell, chloroplastic/mitochondrial (cp/mt) MDAR must contribute to the maintenance of redox state of AsA pool significantly. Under optimal growth condition, the appearance of cp/mt MDAR knockout line of Arabidopsis selected from the Tag-line pool of the Kazusa DNA Research Institute did not differ from that of wild type. Moreover, MDAR specific activity and AsA content were not different between the wild type and the knockout line. However, the knockout line had about 2-fold higher specific activity of superoxide dismutase than the wild type did.