Abstract
SUMMARY: *Apoplastic ascorbate has been proposed to confer resistance to oxidative stresses, e.g. ozone. We investigated reactive oxygen species (ROS)-induced secretion and catabolism of ascorbate. *Late-growth-phase cultured cells of rose and Arabidopsis were preloaded with [(14)C]ascorbate. Radiolabelled metabolites and secretion products were analysed by high-voltage electrophoresis. *In both species, exogenous 1 mM hydrogen peroxide (H(2)O(2)) rapidly stimulated [(14)C]ascorbate and [(14)C]dehydroascorbate accumulation in the medium (apoplast). Net (14)C export was most rapid within 100 s of washing, and often showed superimposed pulses, of c. 10-s duration, whose amplitude was greater after H(2)O(2) treatment. Oxidative stress did not cause indiscriminate metabolite leakage from the cells. H(2)O(2) caused c. 20-40% of the intracellular [(14)C]ascorbate to be irreversibly catabolized to [(14)C]oxalyl-threonate and related products; however, the great majority of the extracellular radioactivity remained as [(14)C]ascorbate and [(14)C]dehydroascorbate. Much of the apoplastic dehydroascorbate was probably reabsorbed by the cells and reduced back to ascorbate. *The data show that exported ascorbate can serve an apoplastic antioxidant role in these late-growth-phase cells without being irreversibly lost, whereas in early-growth-phase cells most extracellular ascorbate is irreversibly degraded. In conclusion, cultured plant cells can respond actively to oxidative stress by reversibly exporting ascorbate into the apoplast.
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Claims 8
Claim · model-written summary
Hydrogen peroxide rapidly stimulated ascorbate and dehydroascorbate accumulation outside cells in both species.
- Taxon
- rose and Arabidopsise1
- Treatment
- exogenous 1 mM hydrogen peroxide (H(2)O(2))e0
- Outcome
- [(14)C]ascorbate and [(14)C]dehydroascorbate accumulation in the medium (apoplast)e0
- Direction
- stimulatede0
Not reportedComparator
Verbatim
e0“In both species, exogenous 1 mM hydrogen peroxide (H(2)O(2)) rapidly stimulated [(14)C]ascorbate and [(14)C]dehydroascorbate accumulation in the medium (apoplast).”
e1“rose and Arabidopsis”
Claim · model-written summary
Net carbon export was fastest within 100 seconds of washing.
Verbatim
e0“Net (14)C export was most rapid within 100 s of washing”
e1“rose and Arabidopsis”
Claim · model-written summary
Export often pulsed for around 10 seconds, with greater pulse amplitude after peroxide treatment.
- Taxon
- rose and Arabidopsise1
- Treatment
- H(2)O(2) treatmente0
- Outcome
- amplitudee0
- Direction
- greatere0
- Value
- c. 10-s duratione0
Not reportedComparator
Verbatim
e0“often showed superimposed pulses, of c. 10-s duration, whose amplitude was greater after H(2)O(2) treatment”
e1“rose and Arabidopsis”
Claim · model-written summary
Oxidative stress did not cause indiscriminate metabolite leakage.
- Taxon
- rose and Arabidopsise1
- Treatment
- Oxidative stresse0
- Outcome
- indiscriminate metabolite leakagee0
- Direction
- did not causee0
Not reportedComparator
Verbatim
e0“Oxidative stress did not cause indiscriminate metabolite leakage from the cells.”
e1“rose and Arabidopsis”
Claim · model-written summary
Peroxide irreversibly catabolized roughly 20–40% of intracellular ascorbate.
- Taxon
- rose and Arabidopsise1
- Treatment
- H(2)O(2)e0
- Outcome
- intracellular [(14)C]ascorbate to be irreversibly catabolizede0
- Direction
- causede0
- Value
- c. 20-40%e0
Not reportedComparator
Verbatim
e0“H(2)O(2) caused c. 20-40% of the intracellular [(14)C]ascorbate to be irreversibly catabolized to [(14)C]oxalyl-threonate and related products”
e1“rose and Arabidopsis”
Claim · model-written summary
Most extracellular radioactivity remained as ascorbate and dehydroascorbate.
Verbatim
e0“the great majority of the extracellular radioactivity remained as [(14)C]ascorbate and [(14)C]dehydroascorbate”
e1“rose and Arabidopsis”
Claim · model-written summary
Apoplastic dehydroascorbate was probably reabsorbed and reduced to ascorbate.
Verbatim
e0“Much of the apoplastic dehydroascorbate was probably reabsorbed by the cells and reduced back to ascorbate.”
e1“rose and Arabidopsis”
Claim · model-written summary
Early-growth-phase cells irreversibly degraded most extracellular ascorbate.
Verbatim
e0“in early-growth-phase cells most extracellular ascorbate is irreversibly degraded”
e1“rose and Arabidopsis”
The same questions in other papers
hydrogen peroxide · molecular: metabolites · ArabidopsisPositive and negative results
1 paper in the same direction as this paper · 6 in the opposite direction
- negative
- no effect
- no effect
4 papers more in this group
See all 8 papers →oxidative · molecular: metabolites · ArabidopsisResults agree
1 paper in the same direction as this paper
- negative
Claims are grouped by organism, treatment and what was measured or targeted. A paper counts as positive when any of its claims in the group is positive.