NICOTIANA TABACUM NADP-MALIC ENZYME ISOFORMS: CLONING AND bIOLOGICAL ROLE ANALYSIS

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

Rosario, Argentina

Congreso; XLII Reunión Anual de la Sociedad Argentina de Investigación en Bioquímica y Biología Molecular; 2006

NADP-Malic Enzyme (NADP-ME, EC 1.1.1.40) catalyzes theoxidative decarboxylation of L-malate producing pyruvate, CO2and NADPH. In plants, the most studied is the isoform involved incarbon fixation in bundle sheath chloroplasts of some C4 plantsand in cytosol of some Crassulacean Acid Metabolism plants(CAM). Although some NADP-MEs have been found in cytosoland plastids of different tissues of C3, C4 and CAM plants, thebiological role remains elusive. The presence of a NADP-MEisoform in stems of vascular bundles and petioles of Nicotianatabacum was proposed to be related to the occurrence of a C4-like cycle. To test this hypothesis and to characterize N. tabacumNADP-ME isoforms, cDNAs encoding two NADP-MEs wereisolated from roots, stems, leaves and flowers. The completecDNAs isolated from leaves (Ntnadp-me 1-2, GenBankDQ923119, DQ923118) were cloned and expressed in E. coliand the proteins are being biochemically characterized. Theresponse of each isoform against different biotic and abioticstresses in different tissues is being evaluated through Real TimePCR and activity assays. Computational sorting predictionprograms indicate that NtNADP-ME1 contains a putative plastidicpeptide transit directing the protein to the plastids whereasNtNADP-ME2 do not possess any predicted organellar targetingsequence, being cytosolic.