Nitrite is the driver, phytohormones are modulators while NO and H2O2 act as promoters of NO2-induced cell death.
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 NO2induced cell death in a dose-dependent manner. No leaf symptoms were visible after fumigation for 1 h with 10 parts per million (ppm) NO2However, 20 ppm NO2caused necrotic lesion formation and 30 ppm NO2complete leaf collapse, which had already started during the 1 h fumigation period. NO2fumigation 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 NO2fumigation. 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 NO2than wild-type plants. Accordingly, experiments with specific scavengers confirmed that NO and H2O2are 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 NO2It 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 NO2and cell death signaling in large-scale mutant screens.
Institute of Biochemical Plant Pathology, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany.
Dörte
D
Kasten
Max Planck Institute for Chemical Ecology, Department Bioorganic Chemistry, Hans-Knöll-Straße 8, D-07745 Jena, Germany.
Axel
A
Mithöfer
Institute of Biochemical Plant Pathology, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany.
Elisabeth
E
Georgii
Research Unit Environmental Simulation, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany.
Hans
H
Lang
Institute of Biochemical Plant Pathology, Helmholtz Zentrum München, German Research Center for Environmental Health, Ingolstädter Landstraße 1, D-85764 Neuherberg, Germany.
Jörg
J
Durner
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.
Frank
0000-0002-6079-6800
F
Gaupels
D017360:Arabidopsis / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D016923:Cell Death / Q000187:drug effects* / Q000502:physiology; D004305:Dose-Response Relationship, Drug; D006861:Hydrogen Peroxide / Q000378:metabolism*; D009569:Nitric Oxide / Q000378:metabolism* / Q000502:physiology; D009573:Nitrites / Q000378:metabolism*; D009585:Nitrogen Dioxide / Q000494:pharmacology*; D010937:Plant Growth Regulators / Q000502:physiology*; D018515:Plant Leaves / Q000187:drug effects / Q000378:metabolism / Q000502:physiology; D020156:Salicylic Acid / Q000378:metabolism
D009573:Nitrites; D010937:Plant Growth Regulators; D009569:Nitric Oxide; D006861:Hydrogen Peroxide; D020156:Salicylic Acid; D009585:Nitrogen Dioxide

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