INSTITUTO DE FISIOLOGIA VEGETAL
Unidad Ejecutora - UE
congresos y reuniones científicas
Synthesis of ascorbic acid: overexpression of L-galactono-1,4-lactone dehydrogenase in Arabidopsis thaliana
GERGOFF GROZEFF, GUSTAVO; SCHERTL, PETER; CÓRDOBA, JUAN PABLO; ZABALETA, EDUARDO; BRAUN, HANS-PETER; BARTOLI, CARLOS GUILLERMO
Foz de Iguazú
Congreso; 11th International Congress of Plant Molecular Biology; 2015
Ascorbicacid (AA) is one of the most important soluble antioxidants in plants, while itis also a vitamin for human diet. The pathway of its synthesis is a complexnet, which converges in the last step, the oxidation of theL-galactono-1,4-lactone (GL) to produce AA. This reaction is catalyzed by themitochondrial enzyme GL dehydrogenase (GLDH) and the oxidation of GL feedselectrons into the mitochondrial electron transport chain This enzyme islocated in the membrane arm of the mitochondrial complex I and oxidizesL-galactono-1,4-lactone. Several works have been made, but the role of GLDH regulationin the AA synthesis is not clear yet.This work studies the regulationof GLDH activity by the interaction with other mitochondrial proteins. Arabidopsisplants were transformed with a 35S::GLDH::c-mycconstruct, for the identification of proteins interacting with GLDH. Two GLDH overexpressing lines were chosen. One-dimensional SDS-PAGE andtwo-dimensional BN/SDS-PAGE was performed to find the position of GLDH in bothlines. It was found that one of the lines overexpresses GLDH out ofmitochondria (named line 43) and the other one in mitochondria; a portion of GLDH,but not all, coupled to mitochondrial complex I (line 49). Partof the work is presented here showing the consequences of GLDH overexpression ineither in or out of plant mitochondria for some physiological processes: Invivo activity of GLDH, content of AA and glutathione with their respective redoxstates, net photosynthesis, photosystem II potential quantum yield andrespiration where measured. GLDH in vivo activity was 3.5 timeshigher in line 49, but line 43 showed no differences compared to the WT.Content of AA showed a 23 % decrease in line 49 but line 43 showed nodifferences with the WT. The redox state of AA was modified in Line 49, showinga 32 % increase in the oxidized form, compared to the WT. Content and redoxstate of gluthatione was not changed. Net Photosynthesis measured as CO2assimilation was enhanced 10 % in line 49 (but not in 43) compared to the WT.In contrast, photosystem II potential quantum yield was not modified in the twotransgenic lines. Similarly, respiration had no statistical differences.These results suggest that the enzyme has to belocalized in mitochondria to get activity. In addition, the excess of GLDH inmitochondria might disturb its activity since alterations are observed in AAcontent and redox state. The increase of photosynthesis in line 49 may be aconsequence of mitochondrial modifications not detected in this work. Furtherstudies must be done to clarify the effects on chloroplast and mitochondrial activities.