Regulation of ascorbic acid synthesis in plants

BARTOLI CG; GÓMEZ F; FERNÁNDEZ L; FOYER C

Buenos Aires, Argentina

Congreso; XII Biennial Meeting of the Society for Free Radical Research International; 2004

Society for Free Radical Research International

The common final step in the synthesis of ascorbic acid through either galactose or galacturonic acid pathways is the oxidation of L-galactone-1,4- lactone. This reaction takes place in plant mitochondria and is closely link to the electron transport chain. This work is aimed to demonstrate that ascorbate biosynthesis is controlled by mitochondrial operation. High irradiances produce progressive increments of ascorbic acid content in leaves of Arabidopsis thaliana. While isolated mitochondria from any light treatment show similar NADH-dependent O2 uptake, malate-pyruvate- and succinate-dependent respiration were increased suggesting that the induction of Complex I and II would contribute to the synthesis of ascorbate under high light conditions. Salicylhydroxamic acid that directly reduces cytochrome c or the presence of high NADH concentration reduced the capacity of isolated plant mitochondria to synthesize ascorbic acid. These results indicate that the availability of oxidized cytochrome c is an important requirement for the synthesis of this antioxidant. Taken as a whole these data demonstrate that ascorbic acid synthesis is controlled by mitochondrial metabolism when plants are subjected to a modifying environment.