Early production and scavenging of hydrogen peroxide in the apoplast of sunflower plants exposed to ozone

• Published in: Journal of experimental botany 2003-11, Vol.54 (392), p.2529-2540
• Main Authors: Ranieri, A., Castagna, A., Pacini, J., Baldan, B., Mensuali Sodi, A., Soldatini, G. F.
• Format: Article
• Language: English
• Subjects: Animal and plant ecology; Animal, plant and microbial ecology; Autoecology; Biological and medical sciences; Cell Membrane - enzymology; Cell membranes; Cell walls; Enzymes; ethylene; Free Radical Scavengers - metabolism; Fumigation; Fundamental and applied biological sciences. Psychology; Helianthus - drug effects; Helianthus - physiology; hydrogen peroxide; Hydrogen Peroxide - metabolism; Key words: Ascorbate peroxidase; Kinetics; NAD(P)H Dehydrogenase (Quinone) - metabolism; NAD(P)H oxidase; NADH, NADPH Oxidoreductases - metabolism; NADPH Oxidases; Non agrochemicals pollutants; Oxidases; Ozone; Ozone - pharmacology; peroxidases; Phytopathology. Animal pests. Plant and forest protection; Plant cells; Plant Structures - drug effects; Plant Structures - physiology; Plants; Plants and fungi; Pollution effects and side effects of agrochemicals on crop plants and forest trees. Other anthropogenic factors; Pollution effects. Side effects of agrochemicals; Reactive oxygen species; Research Papers: Plants and the Environment; signal transduction; sunflower (Helianthus annuus L.); Sunflowers; Thiobarbituric Acid Reactive Substances - analysis; Time Factors
• ISSN: 0022-0957; 1460-2431; 1460-2431
• DOI: 10.1093/jxb/erg270

The present work set out to define the processes involved in the early O3‐induced H2O2 accumulation in sunflower plants exposed to a single pulse of 150 ppb of O3 for 4 h. Hydrogen peroxide accumulation only occurred in the apoplast and this temporally coincided with the fumigation period. The inhibitor experiments suggested that both the plasma membrane‐bound NAD(P)H oxidase complex and cell‐wall NAD(P)H PODs contributed to H2O2 generation. To investigate the mechanisms responsible for O3‐induced H2O2 accumulation further, both production and scavenging of H2O2 were investigated in the extracellular matrix after subcellular fractionation. The results indicated that H2O2 accumulation is a complex and highly regulated event requiring the time‐dependent stimulation and down‐regulation of differently located enzymes, some of which are involved in H2O2 generation and degradation, not only during the fumigation period but also in the subsequent recovery period in non‐polluted air. Owing to the possible interplay between H2O2 and ethylene, the time‐course of ethylene emission was analysed too. Ethylene was rapidly emitted following O3 exposure, but it declined to control values as early as after 4 h of exposure. The early contemporaneous detection of increased ethylene and H2O2 levels after 30 min of exposure does not allow a clear temporal relationship between these two signalling molecules to be established.