Abstract
Erythroascorbic acid (eAsA), a C5 analogue of ascorbic acid (AsA), has been reported to act as an antioxidant in yeasts similar to AsA in higher plants. Using yeast as a model organism to study AsA metabolism in plants, we studied the effect of oxidized eAsA on defence against oxidative stresses.
AsA oxidase (ASO) cDNA from tobacco without coding region for its transit peptide and dehydroascorbate reductase (DHAR) from rice on pFL61 were introduced to S. cerevisiae YPH250. Their expressions were referred from the enzymatic activities in soluble extracts from transformants. Hydrogen peroxide sensitivity and 2',7'-dichlorofluoroscein diacetate fluorescence in Mid-log phase were the highest in DHAR-introduced cells and the lowest in ASO-introduced cells, which strongly shows that eAsA itself does not act as an antioxidant but its oxidized form activates the other antioxidtive system(s) in physiological conditions.
