Maize cytosolic NADP-malic enzyme (ZmCytNADP-ME): a phylogenetically distant isoform specifically expressed in embryo and emerging roots

ENRIQUE DETARSIO; VERÓNICA G. MAURINO; CLARISA E. ALVAREZ; GABRIELA L. MÜLLER; CARLOS S. ANDREO; MARÍA F. DRINCOVICH

PLANT MOLECULAR BIOLOGY

Institute of Plant Science

Lugar: Zurich; Año: 2008 vol. 68 p. 355 - 367

0167-4412

Two maize plastidic NADP-malic enzymeisoforms have been characterized: the bundle sheath-locatedphotosynthetic isoform (ZmC4-NADP-ME) and aconstitutively expressed one (Zm-nonC4-NADP-ME). Inthis work, the characterization of the first maize cytosolicNADP-ME (ZmCytNADP-ME) is presented, which transcriptis exclusively found in embryo and emergingroots. ZmCytNADP-ME expression in roots decreaseswith development, while Zm-nonC4-NADP-ME increasesconcomitantly. On the other hand, ZmCytNADP-MEaccumulation is differentially modulated by several stressconditions and shows coordination with that of Zm-nonC4-NADP-ME in maize young roots. Recombinant ZmCyt-NADP-ME displays clearly distinct kinetic parameters andmetabolic regulation than the plastidic isoforms. The particularproperties and the specific-expression pattern of thisnovel isoform suggest that it may be involved in the controlof cytosolic malate levels in emerging roots, e.g. duringhypoxia. ZmCytNADP-ME is phylogenetically related toother cytosolic mono and dicot NADP-MEs, and dataindicate that it belongs to an ancestral unique group amongplant NADP-MEs