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Plant Sci. 2015 Nov;240:193-203. doi: 10.1016/j.plantsci.2015.09.015. Epub 2015 Sep 25.

Enhanced cytosolic NADP-ME2 activity in A. thaliana affects plant development, stress tolerance and specific diurnal and nocturnal cellular processes.

Author information

1
Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI), Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina.
2
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.
3
Centro de Estudios Fotosintéticos y Bioquímicos (CEFOBI), Universidad Nacional de Rosario, Suipacha 531, 2000 Rosario, Argentina. Electronic address: gerrard@cefobi-conicet.gov.ar.

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.

KEYWORDS:

NADP-malic enzyme; Organic acids; Osmotic stress; Plant homeostasis

PMID:
26475199
DOI:
10.1016/j.plantsci.2015.09.015
[Indexed for MEDLINE]

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