Nicotiana tabacum NADP-malic enzyme isoforms: cloning and biological role analysis

MÜLLER, GABRIELA LETICIA; LARA, MARÍA VALERIA; DRINCOVICH, MARÍA FABIANA; ANDREO, CARLOS SANTIAGO

Rosario

Congreso; XLII Reunión Anual de SAIB; 2006

Sociedad Argentina de Investigación Bioquímica y Biología Molecular (SAIB)

NADP-Malic Enzyme (NADP-ME, EC 1.1.1.40) catalyzes the oxidative decarboxylation of L-malate producing pyruvate, CO2 and NADPH. In plants, the most studied is the isoform involved in carbon fixation in bundle sheath chloroplasts of some C4 plants and in cytosol of some Crassulacean Acid Metabolism plants (CAM). Although some NADP-MEs have been found in cytosol and plastids of different tissues of C3, C4 and CAM plants, the biological role remains elusive. The presence of a NADP-ME isoform in stems of vascular bundles and petioles of Nicotiana tabacum was proposed to be related to the occurrence of a C4-like cycle. To test this hypothesis and to characterize N. tabacum NADP-ME isoforms, cDNAs encoding two NADP-MEs were isolated from roots, stems, leaves and flowers. The complete cDNAs isolated from leaves (Ntnadp-me 1-2, GenBank DQ923119, DQ923118) were cloned and expressed in E. coli and the proteins are being biochemically characterized. The response of each isoform against different biotic and abiotic stresses in different tissues is being evaluated through Real Time PCR and activity assays. Computational sorting prediction programs indicate that NtNADP-ME1 contains a putative plastidic peptide transit directing the protein to the plastids whereas NtNADP-ME2 do not possess any predicted organellar targeting sequence, being cytosolic.