title: Enhanced cytosolic NADP-ME2 activity in A. thaliana affects plant development, stress tolerance and specific diurnal and nocturnal cellular processes.
abstract: Arabidopsis thaliana has four NADP-dependent malic enzymes (NADP-ME 1-4) for reversible malate decarboxylation, with NADP-ME2 being the only cytosolic isoform ubiquitously expressed and responsible for most of the total activity. In this work, we further investigated its physiological function by characterizing Arabidopsis plants over-expressing NADP-ME2 constitutively. In comparison to wild type, these plants exhibited reduced rosette and root sizes, delayed flowering time and increased sensitivity to mannitol and polyethylene glycol. The increased NADP-ME2 activity led to a decreased expression of other ME and malate dehydrogenase isoforms and generated a redox imbalance with opposite characteristics depending on the time point of the day analyzed. The over-expressing plants also presented a higher content of C4 organic acids and sugars under normal growth conditions. However, the accumulation of these metabolites in the over-expressing plants was substantially less pronounced after osmotic stress exposure compared to wild type. Also, a lower level of several amino acids and osmoprotector compounds was observed in transgenic plants. Thus, the gain of NADP-ME2 expression has profound consequences in the modulation of primary metabolism in A. thaliana, which reflect the relevance of this enzyme and its substrates and products in plant homeostasis.
authors.affiliation: Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI), Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina.
authors.forename: Mariana B
authors.initials: MB
authors.lastname: Badia
authors.affiliation: Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI), Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina.
authors.forename: Cintia L
authors.initials: CL
authors.lastname: Arias
authors.affiliation: Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI), Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina.
authors.forename: Marcos A
authors.initials: MA
authors.lastname: Tronconi
authors.affiliation: Institute of Developmental and Molecular Biology of Plants, Plant Molecular Physiology and Biotechnology Group, Heinrich-Heine-Universität, Universitätsstr. 1, and Cluster of Excellence on Plant Sciences (CEPLAS), 40225 Düsseldorf, Germany.
authors.forename: Verónica G
authors.initials: VG
authors.lastname: Maurino
authors.affiliation: Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI), Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina.
authors.forename: Carlos S
authors.initials: CS
authors.lastname: Andreo
authors.affiliation: Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI), Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina.
authors.forename: María F
authors.initials: MF
authors.lastname: Drincovich
authors.affiliation: Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI), Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina. Electronic address: gerrard@cefobi-conicet.gov.ar.
authors.forename: Mariel C Gerrard
authors.initials: MC
authors.lastname: Wheeler
mesh_terms: D017360:Arabidopsis / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D002940:Circadian Rhythm; D015971:Gene Expression Regulation, Enzymologic; D018506:Gene Expression Regulation, Plant; D050538:Malate Dehydrogenase (NADP+) / Q000235:genetics* / Q000378:metabolism; D030821:Plants, Genetically Modified / Q000235:genetics / Q000254:growth & development / Q000502:physiology; D013312:Stress, Physiological
chemical_list: D029681:Arabidopsis Proteins; C000609452:NADP-ME2 protein, Arabidopsis; D050538:Malate Dehydrogenase (NADP+)
keywords: NADP-malic enzyme; Organic acids; Osmotic stress; Plant homeostasis