Metabolic changes induced by high NADP-ME activity in Arabidopsis thaliana chloroplasts.

MARIANA SAIGO; RODRIGO D´ANDREA; HOLGER FAHNENSTICH; MARÍA F. DRINCOVICH; CARLOS ANDREO; VERÓNICA MAURINO

Pinamar, Argentina

Congreso; Sociedad Argentina de Investigación en Bioquímica y Biología Molecular XLI Reunión Anual; 2005

Sociedad Argentina de Investigación en Bioquímica y Biología Molecular

Arabidopsis thaliana (Columbia-0 ecotype) was transformed with a vector containing the maize chloroplastic NADP-malic enzyme (NADP-ME) cDNA under the control of 35SCaMV promoter. This enzyme catalyzes the oxidative decarboxylation of malate, generating pyruvate, CO2 and NADPH. The line with the highest expression level showed a 30-fold increase in NADP-ME activity. When grown under different light intensities, morphological differences between wild type and transgenic lines were evident. Chlorophyll content as well as photosynthetic performance indicators like Fv/Fm and FPSII were significantly lower for transgenic lines. CO2 assimilation rates measured at increasing light intensities were also different in transgenic lines in comparison with wild type. On the other hand, sugar levels fluctuation during the day-night cycle also varied in plants expressing maize NADP-ME. These results suggest that the presence of a highly active NADP-ME in chloroplasts of A thaliana, could have important effects on the reductive power balance of this organelle, diminishing the efficiency of the overall photosynthetic process and affecting carbohydrate metabolism. These transgenic plants are a useful tool to better understand the regulation of plastid redox poise and related metabolisms.