Effects of Fusaric Acid on Reactive Oxygen Species and Antioxidants in Tomato Cell Cultures

Generation of O2 ± and H2O2 as well as the activities of superoxide dismutase, catalase, ascorbate peroxidase, guaiacol peroxidase, dehydroascorbate reductase and ascorbate content were studied in tomato cell cultures in response to fusaric acid ± a nonspeci®c toxin of phytopathogenic Fusarium species. Toxin treatment resulted in decreased cell viability which was preceded by culture medium alkalinization up to 0.65 pH unit and enhanced extracellular O2 ± production. The H2O2 level was not signi®cantly a€ected. In toxin-treated cultures, a transient, signi®cant increase occurred in intracellular superoxide dismutase, catalase, guaiacol peroxidase and ascorbate peroxidase activities. Fusaric acid-induced ascorbate turnover modulation led to up to a twofold increase in dehydroascorbic acid accumulation, and a decrease in the associated ascorbate redox ratio. It was concomitant with a signi®cant decrease in dehydro- ascorbate reductase activity. These results support previous observations that the pro- and anti-oxidant systems are involved in response to fusaric acid treat- ment although di€erential response of H2O2 and its metabolism-related enzymes between the whole leaf and cell culture assays was found.