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

Autor(en): Hebbelmann, Inga
Selinski, Jennifer
Wehmeyer, Corinna
Goss, Tatjana
Voss, Ingo
Mulo, Paula
Kangasjarvi, Saijaliisa
Aro, Eva-Mari
Oelze, Marie-Luise
Dietz, Karl-Josef
Nunes-Nesi, Adriano
Do, Phuc T.
Fernie, Alisdair R.
Talla, Sai K.
Raghavendra, Agepati S.
Linke, Vera
Scheibe, Renate 
Stichwörter: ANTIOXIDANT DEFENSES; ASCORBATE; CHLOROPLAST; GLUTATHIONE; LIGHT; Malate valve; MESOPHYLL PROTOPLASTS; NADP-malate dehydrogenase; oxidative stress; PHOTORESPIRATION; Plant Sciences; poising mechanisms; REDOX HOMEOSTASIS; THALIANA; THIOREDOXIN REDUCTASE
Erscheinungsdatum: 2012
Herausgeber: OXFORD UNIV PRESS
Journal: JOURNAL OF EXPERIMENTAL BOTANY
Volumen: 63
Ausgabe: 3
Startseite: 1445
Seitenende: 1459
Zusammenfassung: 
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 C-3 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.
ISSN: 00220957
DOI: 10.1093/jxb/err386

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