Abstract
Significance: Plant stress involves redox signaling linked to reactive oxygen species such as hydrogen peroxide (H2O2), which can be generated at high rates in photosynthetic cells. The systems that process H2O2 include catalase (CAT) and the ascorbate–glutathione pathway, but interactions between them remain unclear. Modeling can aid interpretation and pinpoint areas for investigation. Recent Advances: Based on emerging data and concepts, we introduce a new experimentally constrained kinetic model to analyze interactions between H2O2, CAT, ascorbate, glutathione, and NADPH. The sensitivity points required for accurate simulation of experimental observations are analyzed, and the implications for H2O2-linked redox signaling are discussed. Critical Issues: We discuss several implications of the modeled results, in particular the following. (i) CAT and ascorbate peroxidase can share the load in H2O2 processing even in optimal conditions. (ii) Intracellular H2O2 concentrations more than the low μM range may rarely occur. (iii) Ascorbate redox turnover is largely independent of glutathione until ascorbate peroxidation exceeds a certain value. (iv) NADPH availability may determine glutathione redox status through its influence on monodehydroascorbate reduction. (v) The sensitivity of glutathione status to oxidative stress emphasizes its potential suitability as a sensor of increased H2O2. Future Directions: Important future questions include the roles of other antioxidative systems in interacting with CAT and the ascorbate–glutathione pathway as well as the nature and significance of processes that achieve redox exchange between different subcellular compartments. Progress in these areas is likely to be favored by integrating kinetic modeling analyses into experimentally based programs, allowing each approach to inform the other.
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Claims 5
Claim · model-written summary
The model suggests CAT and ascorbate peroxidase can share H2O2 processing in optimal conditions.
Verbatim
e0“CAT and ascorbate peroxidase can share the load in H2O2 processing even in optimal conditions.”
e1“Plant stress involves redox signaling”
Claim · model-written summary
The model suggests intracellular H2O2 concentrations above the low micromolar range may be rare.
Verbatim
e0“Intracellular H2O2 concentrations more than the low μM range may rarely occur.”
e1“Plant stress involves redox signaling”
Claim · model-written summary
Modeled ascorbate redox turnover was largely independent of glutathione until ascorbate peroxidation exceeded a threshold.
- Taxon
- Plante1
- Compound
- glutathionee0
- Outcome
- Ascorbate redox turnovere0
- Qualifier
- until ascorbate peroxidation exceeds a certain valuee0
Not reportedDirection
Verbatim
e0“Ascorbate redox turnover is largely independent of glutathione until ascorbate peroxidation exceeds a certain value.”
e1“Plant stress involves redox signaling”
Claim · model-written summary
Modeled NADPH availability may determine glutathione redox status through monodehydroascorbate reduction.
Verbatim
e0“NADPH availability may determine glutathione redox status through its influence on monodehydroascorbate reduction.”
e1“Plant stress involves redox signaling”
Claim · model-written summary
The modeled sensitivity of glutathione status to oxidative stress suggests it could sense increased H2O2.
Verbatim
e0“The sensitivity of glutathione status to oxidative stress emphasizes its potential suitability as a sensor of increased H2O2.”
e1“Plant stress involves redox signaling”