Effect of mitochondrial ascorbic acid synthesis on photosynthesis

Abstract

Ascorbic acid (AA) is synthesized in plant mitochondria through the oxidation of L-galactono-1,4-lactone (L-GalL) and then distributed to different cell compartments. AA-deficient Arabidopsis thaliana mutants (vtc2) and exogenous applications of L-GalL were used to generate plants with different AA content in their leaves. This experimental approach allows determining specific AA-dependent effects on carbon metabolism. No differences in O2 uptake, malic and citric acid and NADH content suggest that AA synthesis or accumulation did not affect mitochondrial activity; however, L-GalL treatment increased CO2 assimilation and photosynthetic electron transport rate in vtc2 (but not wt) leaves demonstrating a stimulation of photosynthesis after L-GalL treatment. Increased CO2 assimilation correlated with increased leaf stomatal conductance observed in L-GalL-treated vtc2 plants