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J Exp Bot. 2016 Dec;67(22):6337-6349. Epub 2016 Nov 2.

Nitrite is the driver, phytohormones are modulators while NO and H2O2 act as promoters of NO2-induced cell death.

Author information

1
Institute of Biochemical Plant Pathology, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany.
2
Max Planck Institute for Chemical Ecology, Department Bioorganic Chemistry, Hans-Knöll-Straße 8, D-07745 Jena, Germany.
3
Research Unit Environmental Simulation, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany.
4
Institute of Biochemical Plant Pathology, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany frank.gaupels@helmholtz-muenchen.de.

Abstract

This study aimed to understand the molecular mechanisms of nitrogen dioxide (NO2)-induced toxicity and cell death in plants. Exposure of Arabidopsis to high concentrations of NO2 induced cell death in a dose-dependent manner. No leaf symptoms were visible after fumigation for 1 h with 10 parts per million (ppm) NO2 However, 20 ppm NO2 caused necrotic lesion formation and 30 ppm NO2 complete leaf collapse, which had already started during the 1 h fumigation period. NO2 fumigation resulted in a massive accumulation of nitrite and in protein modifications by S-nitrosylation and tyrosine nitration. Nitric oxide (NO) at 30 ppm did not trigger leaf damage or any of the effects observed after NO2 fumigation. The onset of NO2-induced cell death correlated with NO and hydrogen peroxide (H2O2) signaling and a decrease in antioxidants. NO- and H2O2-accumulating mutants were more sensitive to NO2 than wild-type plants. Accordingly, experiments with specific scavengers confirmed that NO and H2O2 are essential promoters of NO2-induced cell death. Leaf injection of 100 mM nitrite caused an increase in S-nitrosylation, NO, H2O2, and cell death suggesting that nitrite functioned as a mediator of NO2-induced effects. A targeted screening of phytohormone mutants revealed a protective role of salicylic acid (SA) signaling in response to NO2 It was also shown that phytohormones were modulators rather than inducers of NO2-induced cell death. The established experimental set-up is a suitable system to investigate NO2 and cell death signaling in large-scale mutant screens.

KEYWORDS:

S-nitrosothiols; Antioxidative system; H2O2 ; NO; NO2 ; cell death; nitrite; phytohormones; tyrosine nitration.

PMID:
27811003
DOI:
10.1093/jxb/erw401
[Indexed for MEDLINE]

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