Gain of cytosolic NADP-ME activity impacts on primary metabolism and stress tolerance of A. thaliana

BADIA, M. B.; ARIAS, C. L.; TRONCONI, M. A.; MAURINO, V. G.; ANDREO, C. S.; DRINCOVICH, M. F.; GERRARD WHEELER, M. C.

Mendoza

Congreso; XLVIII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2012

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

NAD(P)-malic enzyme (ME) catalyzes the reversible oxidative decarboxylation of malate to pyruvate, CO2 and NAD(P)H and is present as a multigene family in Arabidopsis thaliana. Phenotypic and molecular characterization of plants over-expressing cytosolic NADP-ME2 was carried out. These plants exhibited lower rosette weight and root length relative to wild-type, added to an increased sensitivity to mannitol treatment on MS-plates or irrigation with PEG on soil-grown plants. Interestingly, the increased NADP-ME activity led to a decreased expression of the others constitutive ME isoforms and of another malate metabolism related enzyme, the malate dehydrogenase. In addition, this line presented higher content of organic acids and sugars relative to wild-type under typical growth conditions. However, the accumulation of these metabolites was substantially less pronounced after osmotic stress exposure. This indicates that altering malate metabolism by raising NADP-ME2 activity has profound consequences for the response of the entire primary metabolism upon normal and stress conditions. Overall, the gain of NADP-ME activity produces changes in gene expression, enzymatic activities and metabolite levels which reflect the relevance of this enzyme in the organic acid plant metabolism.