Journal
JOURNAL OF EXPERIMENTAL BOTANY
Volume 54, Issue 392, Pages 2529-2540Publisher
OXFORD UNIV PRESS
DOI: 10.1093/jxb/erg270
Keywords
Key words; Ascorbate peroxidase; ethylene; hydrogen peroxide; NAD(P)H oxidase; ozone; peroxidases; reactive oxygen species; signal transduction; sunflower (Helianthus annuus L; )
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The present work set out to define the processes involved in the early O-3-induced H2O2 accumulation in sunflower plants exposed to a single pulse of 150 ppb of O-3 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 O-3-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 O-3 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.
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