Abstract
Changes in the total pool sizes of ascorbate and glutathione and their degree of oxidation as well as the activities of ascorbate peroxidase, dehydroascorbate reductase, glutathione reductase and glutathione transferase in tomato leaves after Botrytis cinerea infection have been studied. In infected leaves the concentration of reduced ascorbate was similar to that in control. A transient increase in dehydroascorbate content (55% above the control) and a decrease in the ascorbate redox status were observed only 3 days after inoculation. In the diseased leaves we found a significant progressive decrease, up to ∼50% 5 days after inoculation, in the reduced glutathione content while the oxidized glutathione concentration remained unaffected. Although a decline in reduced glutathione content was detected the ascorbate and glutathione redox ratios were maintained high up to the 5th day after inoculation. B. cinerea infection enhanced ascorbate peroxidase and glutathione reductase activities. Dehydroascorbate reductase activity was significantly decreased when compared with control, but its activity level in the inoculated leaves stayed rather constant. Total glutathione transferase activity remained unchanged. In the diseased tissues statistically significant ( P<0.05) linear correlations between glutathione reductase and ascorbate peroxidase activities were found to occur 4 and 5 days after inoculation and ascorbate peroxidase activity was correlated with the total glutathione level and reduced glutathione content on the 4th day. The decreased reduced glutathione content found in the infected leaves could be a limiting factor for operation of the ascorbate-glutathione cycle related enzymes at the advanced stages of infection development.
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