Conditional oxidative stress responses in the Arabidopsis photorespiratory mutant cat2 demonstrate that redox state is a key modulator of daylength‐dependent gene expression, and define photoperiod as a crucial factor in the regulation of H₂O₂‐induced cell death

Abstract

SummaryPhotorespiration is a light-dependent source of H 2 O 2 in the peroxisomes, where concentrations of this signalling molecule are regulated by catalase. Growth of Arabidopsis knock-out mutants for CATALASE2 (cat2) in ambient air caused severely decreased rosette biomass, intracellular redox perturbation and activation of oxidative signalling pathways. These effects were absent when cat2 was grown at high CO 2 levels to inhibit photorespiration, but were re-established following a subsequent transfer to air. Growth of cat2 in air at different daylengths revealed that photoperiod is a critical determinant of the oxidative stress response. Decreased growth was observed in 8-h, 12-h and 16-h photoperiods, but lesion development was dependent on long days. Experiments at different light fluence rates showed that cell death in cat2 was linked to long days and not to total light exposure or the severity of oxidative stress. Perturbed intracellular redox state and oxidative signalling pathway induction were more prominent in short days than in long days, as evidenced by glutathione status and induction of defence genes and oxidative stress-responsive transcripts. Similar daylength-dependent effects were observed in the response of mature plants transferred from short days in high CO 2 conditions to ambient air conditions. Prior growth of plants with short days in air alleviated the cat2 cell-death phenotype in long days. Together, the data reveal the influence of photoperiodic events on redox signalling, and define distinct photoperiod-dependent strategies in the acclimation versus cell-death decision in stress conditions.

Generation of Hydrogen Peroxide in Chloroplasts of Arabidopsis Overexpressing Glycolate Oxidase as an Inducible System to Study Oxidative Stress

“…Similar features were observed in cat2 and apx1 mutants (Pnueli et al, 2003;Queval et al, 2007). It is feasible that the enhanced levels of H 2 O 2 in these plants affected the expression of transcription factors involved in the regulation of plant growth and flowering.…”

Unraveling the Tapestry of Networks Involving Reactive Oxygen Species in Plants

“…The evaluation of the Arabidopsis catalase2 mutants at different day lengths has revealed that photoperiod is a critical determinant of the oxidative stress response, with lesion development being enhanced in plants grown under long-day conditions (Queval et al, 2007). Singlet oxygen-induced cell death depends on the blue light/UVA-specific photoreceptor cryptochrome and differs from PCD triggered by H 2 O 2 /O 2 2 (Danon et al, 2006).…”

Singlet Oxygen Is the Major Reactive Oxygen Species Involved in Photooxidative Damage to Plants

“…In recent years, the production of various transgenic Arabidopsis (Arabidopsis thaliana) plants with compromised levels of specific antioxidant enzymes and the identification of the conditional fluorescent ( flu) mutant provided important tools to assess the specific effects of O 2 2. , H 2 O 2 , and 1 O 2 within a particular subcellular compartment (Dat et al, 2003;op den Camp et al, 2003;Pnueli et al, 2003;Rizhsky et al 2003;Vandenabeele et al, 2004;Wagner et al, 2004;Queval et al, 2007). For example, with catalase-deficient [Cat(2)] plants, the signaling effects of increased photorespiratory H 2 O 2 levels could be identified (Dat et al, 2003;Vandenabeele et al, 2004;Queval et al, 2007).…”