Journal Article

Multiple strategies to prevent oxidative stress in Arabidopsis plants lacking the malate valve enzyme NADP-malate dehydrogenase

Raghavendra, Agepati S., Kangasjärvi, Saijaliisa, Mulo, Paula, Scheibe, Renate, Talla, Sai K., Wehmeyer, Corinna, Nunes-Nesi, Adriano, Dietz, Karl-Josef, Fernie, Alisdair R., Goss, Tatjana, Selinski, Jennifer, Aro, Eva-Mari, Voss, Ingo, Do, Phuc T., Linke, Vera, Hebbelmann, Inga, Oelze, Marie-Luise

2012

Overview

The nuclear-encoded chloroplast NADP-dependent malate dehydrogenase (NADP-MDH) is a key enzyme controlling the malate valve, to allow the indirect export of reducing equivalents. Arabidopsis thaliana (L.) Heynh. T-DNA insertion mutants of NADP-MDH were used to assess the role of the light-activated NADP-MDH in a typical C3 plant. Surprisingly, even when exposed to high-light conditions in short days, nadp-mdh knockout mutants were phenotypically indistinguishable from the wild type. The photosynthetic performance and typical antioxidative systems, such as the Beck-Halliwell-Asada pathway, were barely affected in the mutants in response to high-light treatment. The reactive oxygen species levels remained low, indicating the apparent absence of oxidative stress, in the mutants. Further analysis revealed a novel combination of compensatory mechanisms in order to maintain redox homeostasis in the nadp-mdh plants under high-light conditions, particularly an increase in the NTRC/2-Cys peroxiredoxin (Prx) system in chloroplasts. There were indications of adjustments in extra-chloroplastic components of photorespiration and proline levels, which all could dissipate excess reducing equivalents, sustain photosynthesis, and prevent photoinhibition in nadp-mdh knockout plants. Such metabolic flexibility suggests that the malate valve acts in concert with other NADPH-consuming reactions to maintain a balanced redox state during photosynthesis under high-light stress in wild-type plants.

• Publisher: Oxford University Press
• Subject: Arabidopsis / Arabidopsis - enzymology / Arabidopsis - genetics / Arabidopsis - metabolism / Arabidopsis thaliana / Biological and medical sciences / C3 plants / enzymology / Fundamental and applied biological sciences. Psychology / genetics / homeostasis / knockout mutants / malate dehydrogenase / malate dehydrogenase (NADP) / Malate Dehydrogenase (NADP+) - genetics / metabolism / Oxidation-Reduction / oxidative stress / Oxidative Stress - genetics / Oxidative Stress - physiology / peroxiredoxin / photoinhibition / photorespiration / Photosynthesis / Photosynthesis - genetics / Photosynthesis - physiology / physiology / Plant physiology and development / plant stress / Plants, Genetically Modified / Plants, Genetically Modified - enzymology / Plants, Genetically Modified - genetics / Plants, Genetically Modified - metabolism / reactive oxygen species / Research Papers / transfer DNA