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Plant Physiol. 2017 Jun;174(2):956-971. doi: 10.1104/pp.17.00317. Epub 2017 Apr 5.

Cytosolic and Chloroplastic DHARs Cooperate in Oxidative Stress-Driven Activation of the Salicylic Acid Pathway.

Author information

1
Institute of Plant Sciences Paris-Saclay, Unité Mixte de Recherche 9213/Unité Mixte de Recherche 1403, Université Paris-Sud, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Université d'Evry, Université Paris-Diderot, Sorbonne Paris-Cité, 91405 Orsay, France (M.-S.R., S.L., G.C.-I., E.I.-B., A.M., G.N.); and.
2
Unité Mixte de Recherche ECOSYS/Pôle BIOCLIMATOLOGIE, Institut National de la Recherche Agronomique-AgroParisTech, F-78850 Thiverval-Grignon, France (A.T.).
3
Institute of Plant Sciences Paris-Saclay, Unité Mixte de Recherche 9213/Unité Mixte de Recherche 1403, Université Paris-Sud, Centre National de la Recherche Scientifique, Institut National de la Recherche Agronomique, Université d'Evry, Université Paris-Diderot, Sorbonne Paris-Cité, 91405 Orsay, France (M.-S.R., S.L., G.C.-I., E.I.-B., A.M., G.N.); and graham.noctor@u-psud.fr.
4
Unité Mixte de Recherche ECOSYS/Pôle BIOCLIMATOLOGIE, Institut National de la Recherche Agronomique-AgroParisTech, F-78850 Thiverval-Grignon, France (A.T.) graham.noctor@u-psud.fr.

Abstract

The complexity of plant antioxidative systems gives rise to many unresolved questions. One relates to the functional importance of dehydroascorbate reductases (DHARs) in interactions between ascorbate and glutathione. To investigate this issue, we produced a complete set of loss-of-function mutants for the three annotated Arabidopsis (Arabidopsis thaliana) DHARs. The combined loss of DHAR1 and DHAR3 expression decreased extractable activity to very low levels but had little effect on phenotype or ascorbate and glutathione pools in standard conditions. An analysis of the subcellular localization of the DHARs in Arabidopsis lines stably transformed with GFP fusion proteins revealed that DHAR1 and DHAR2 are cytosolic while DHAR3 is chloroplastic, with no evidence for peroxisomal or mitochondrial localizations. When the mutations were introduced into an oxidative stress genetic background (cat2), the dhar1 dhar2 combination decreased glutathione oxidation and inhibited cat2-triggered induction of the salicylic acid pathway. These effects were reversed in cat2 dhar1 dhar2 dhar3 complemented with any of the three DHARs. The data suggest that (1) DHAR can be decreased to negligible levels without marked effects on ascorbate pools, (2) the cytosolic isoforms are particularly important in coupling intracellular hydrogen peroxide metabolism to glutathione oxidation, and (3) DHAR-dependent glutathione oxidation influences redox-driven salicylic acid accumulation.

PMID:
28381499
PMCID:
PMC5462045
DOI:
10.1104/pp.17.00317
[Indexed for MEDLINE]
Free PMC Article

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