Plastidial NADP-Malic Enzymes from grasses: the evolution of the C4 specific isoforms

MARIANA SAIGO; CLARISA ALVAREZ; CARLOS S. ANDREO; MARÍA F. DRINCOVICH

Mar del Plata

Congreso; Reunión argentina de fisiología vegetal; 2012

Sociedad argentina de fisiología vegetal

Malic enzyme is present in many plant cell compartments such as plastids, cytosoland mitochondria. Particularly relevant is the plastidial isoform that participatesin the C4 cycle providing CO2 to RuBisCO in C4 species. This type of photosynthesisis more frequent among grasses where anatomical preconditioning would havefacilitated the evolution of the C4 syndrome. In maize (C4 grass), thephotosynthetic NADP dependent Malic enzyme (ZmC4-NADP-ME) and the closest relatednon-photosynthetic isoform (ZmnonC4-NADP-ME) are both plastidial but differ inexpression pattern, kinetics and structure. Features like high catalytic efficiency,inhibition by high malate concentration at pH 7.0, redox modulation andtetramerization are characteristic of the photosynthetic NADP-ME. In this work, theproducts of sorghum (C4 grass) and rice (C3 grass) NADP-ME genes, orthologues of theplastidial NADP-MEs from maize, were expressed and characterized. In a globalcomparison, we could identify a small group of residues which may explain thespecial features of C4 enzymes. Overall, the present work presents biochemical andmolecular data that helps to elucidate the changes that took place in the evolutionof C4 NADP-ME in grasses.