title: Distinct but conserved functions for two chloroplastic NADP-malic enzyme isoforms in C3 and C4 Flaveria species.
abstract: In the most common C4 pathway for carbon fixation, an NADP-malic enzyme (NADP-ME) decarboxylates malate in the chloroplasts of bundle sheath cells. Isoforms of plastidic NADP-ME are encoded by two genes in all species of Flaveria, including C3, C3-C4 intermediate, and C4 types. However, only one of these genes, ChlMe1, encodes the enzyme that functions in the C4 pathway. We compared the expression patterns of the ChlMe1 and ChlMe2 genes in developing leaves of Flaveria pringlei (C3) and Flaveria trinervia (C4) and in transgenic Flaveria bidentis (C4). ChlMe1 expression in C4 species increases in leaves with high C4 pathway activity. In the C3 species F. pringlei, ChlMe1 expression is transient and limited to early leaf development. In contrast, ChlMe2 is expressed in C3 and C4 species concurrent with stages in chloroplast biogenesis. Because previous studies suggest that NADP-ME activities generally reflect the level of its mRNA abundance, we discuss possible roles of ChlMe1 and ChlMe2 based on these expression patterns.
authors.affiliation: Department of Molecular, Cellular and Developmental Biology, Yale University, New Haven, Connecticut 06520-8104, USA.
authors.forename: Lien B
authors.initials: LB
authors.lastname: Lai
authors.forename: Lin
authors.initials: L
authors.lastname: Wang
authors.forename: Timothy M
authors.initials: TM
authors.lastname: Nelson
mesh_terms: D019659:Asteraceae / Q000201:enzymology / Q000235:genetics*; D001483:Base Sequence; D002736:Chloroplasts / Q000201:enzymology* / Q000235:genetics; D003001:Cloning, Molecular; D015971:Gene Expression Regulation, Enzymologic / Q000528:radiation effects; D018506:Gene Expression Regulation, Plant / Q000528:radiation effects; D007527:Isoenzymes / Q000235:genetics / Q000378:metabolism; D008027:Light; D008291:Malate Dehydrogenase / Q000235:genetics* / Q000378:metabolism; D008293:Malates / Q000378:metabolism; D008969:Molecular Sequence Data; D010788:Photosynthesis / Q000235:genetics; D045322:Photosynthetic Reaction Center Complex Proteins / Q000235:genetics*; D018515:Plant Leaves / Q000201:enzymology / Q000235:genetics; D016415:Sequence Alignment
chemical_list: D007527:Isoenzymes; D008293:Malates; D045322:Photosynthetic Reaction Center Complex Proteins; C030298:malic acid; D008291:Malate Dehydrogenase; C031917:malate dehydrogenase (oxaloacetate-decarboxylating) (NADP+)