Synthesis of ascorbic acid: overexpression of L-galactono-1,4-lactone dehydrogenase in Arabidopsis thaliana

GERGOFF GROZEFF, G.E.; SCHERTL, PETER; CÓRDOBA, J.P.; BARTOLI, CARLOS G.; ZABALETA, E.; BRAUN, HANS-PETER

Foz de Iguazú

Congreso; 11th International Congress of Plant Molecular Biology; 2015

International Society for Plant Molecular Biology

The Ascorbic acid (AA) synthesis pathway is a complex net, which converges in the oxidation of the L-galactono-1,4-lactone (GL) to produce AA. This reaction is catalyzed by the mitochondrial enzyme GL dehydrogenase (GLDH). GLDH is located in the mitochondrial complex I, but the regulation of GLDH is not clear yet. Arabidopsis plants were transformed with a 35S::GLDH::c-myc construct, for the identification of proteins interacting with GLDH. One-dimensional SDS-PAGE and two-dimensional BN/SDS-PAGE were performed to find the position of GLDH and protein association in two lines. It was found that L43 overexpresses GLDH out of mitochondria and L49 inside mitochondria coupled to complex I (L49). In vivo GLDH activity was 3.5 times higher in L49, but line 43 showed no differences compared to the WT. Content of AA showed a 23 % decrease in L49 but L43 showed no differences with the WT. The redox state of AA was modified in L49, showing a 32 % increase in the oxidized form, compared to the WT. Net Photosynthesis, measured as CO2 assimilation, was enhanced 10 % in L49 (but not L43) compared to the WT. In contrast, respiration was notmodified in the two transgenic lines. These results suggest that the enzyme has to be localized in mitochondria to get activity. The excess of GLDH in mitochondria might disturb its activity since alterations were observed in AA content and redox state. The increase of photosynthesis in L49 may be a consequence of mitochondrial modifications not detected in this work.