Altered osmotic stress response in Arabidopsis thaliana lines with modified levels of malic enzyme

BADIA, MARIANA; ARIAS, C. L.; TRONCONI, M.; MAURINO, VERÓNICA G; ANDREO, CARLOS S; MARIA FABIANA DRINCOVICH; MARIEL GERRARD WHEELER

San Luis

Congreso; XLVII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2011

A. thaliana is an organic acid hyperaccumulator plant species. Among the enzymes that metabolize these compounds one of the most important is malic enzyme (ME), which is present as a multigene family in this model species. In the present work, mutant and over-expressing lines in cytosolic AtNADP-ME2, the isoform that mostly contributes to the ME activity in all organs of the plant, were characterized. Despite the variations in the levels of ME activity, all genetically modified lines exhibited a normal vegetative and reproductive development under typical growth conditions. However, after exposure to different stress conditions that modify the water potential, the plants with increased ME activity were significantly more sensitive to PEG treatment. This differential response was not observed in the treatments of drought stress or high salt concentrations. This over-expressing line presented a higher NAD(P)/NAD(P)H ratio respect to the wild-type and a lower pyridine nucleotide total content, specially at the end of the night. This imbalance in redox status caused by increased ME2 levels could have a deep impact on the defense responses to stress. Thus, ME2 participate in the cellular redox homeostasis, contributing to oxidation and/or reduction of these compounds, given the reversibility of the reaction it catalyzes