Abstract
Ascorbate is not often considered as a signalling molecule in plants. This study demonstrates that, in Arabidopsis roots, exogenous l-ascorbic acid triggers a transient increase of the cytosolic free calcium activity ([Ca2+]cyt.) that is central to plant signalling. Exogenous copper and iron stimulate the ascorbate-induced [Ca2+]cyt. elevation, while cation channel blockers, free radical scavengers, low extracellular [Ca2+], transition metal chelators, and removal of the cell wall inhibit this reaction. These data show that apoplastic redox-active transition metals are involved in the ascorbate-induced [Ca2+]cyt. elevation. Exogenous ascorbate also induces a moderate increase in programmed cell death symptoms in intact roots, but it does not activate Ca2+ influx currents in patch-clamped root protoplasts. Intriguingly, the replacement of gluconate with ascorbate in the patch-clamp pipette reveals a large ascorbate efflux current, which shows sensitivity to the anion channel blocker, anthracene-9-carboxylic acid (A9C), indicative of the ascorbate release via anion channels. EPR spectroscopy measurements demonstrate that salinity (NaCl) triggers the accumulation of root apoplastic ascorbyl radicals in an A9C-dependent manner, confirming that l-ascorbate leaks through anion channels under depolarization. This mechanism may underlie ascorbate release, signalling phenomena, apoplastic redox reactions, iron acquisition, and control the ionic and electrical equilibrium (together with K+ efflux via GORK channels).
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Claims 11
Claim · model-written summary
Exogenous l-ascorbic acid transiently increased cytosolic free calcium activity in Arabidopsis roots.
- Taxon
- Arabidopsis
Arabidopsise0 - Organ / stage
- rootse0
- Treatment
- exogenous l-ascorbic acide0
- Outcome
- cytosolic free calcium activity ([Ca2+]cyt.)e0
- Direction
- increasee0
- Qualifier
- transiente0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in Arabidopsis roots, exogenous l-ascorbic acid triggers a transient increase of the cytosolic free calcium activity ([Ca2+]cyt.)”
Claim · model-written summary
Exogenous copper stimulated ascorbate-induced calcium elevation.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- Exogenous coppere0
- Outcome
- ascorbate-induced [Ca2+]cyt. elevatione0
- Direction
- stimulatee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Exogenous copper and iron stimulate the ascorbate-induced [Ca2+]cyt. elevation”
t0“in Arabidopsis roots”
Claim · model-written summary
Exogenous iron stimulated ascorbate-induced calcium elevation.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- irone0
- Outcome
- ascorbate-induced [Ca2+]cyt. elevatione0
- Direction
- stimulatee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Exogenous copper and iron stimulate the ascorbate-induced [Ca2+]cyt. elevation”
t0“in Arabidopsis roots”
Claim · model-written summary
Cation channel blockers, free radical scavengers, low extracellular calcium, transition metal chelators and cell wall removal inhibited the ascorbate calcium response.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- cation channel blockers, free radical scavengers, low extracellular [Ca2+], transition metal chelators, and removal of the cell walle0
- Outcome
- this reactione0
- Direction
- inhibite0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“cation channel blockers, free radical scavengers, low extracellular [Ca2+], transition metal chelators, and removal of the cell wall inhibit this reaction”
t0“in Arabidopsis roots”
Claim · model-written summary
Apoplastic redox-active transition metals were implicated in the ascorbate-induced calcium elevation.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- ascorbate-induced [Ca2+]cyt. elevatione0
- Qualifier
- apoplastic redox-active transition metalse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“apoplastic redox-active transition metals are involved in the ascorbate-induced [Ca2+]cyt. elevation”
t0“in Arabidopsis roots”
Claim · model-written summary
Exogenous ascorbate moderately increased programmed cell death symptoms in intact roots.
- Taxon
- ArabidopsisArabidopsist0
- Organ / stage
- intact rootse0
- Treatment
- Exogenous ascorbatee0
- Outcome
- programmed cell death symptomse0
- Direction
- increasee0
- Qualifier
- moderatee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Exogenous ascorbate also induces a moderate increase in programmed cell death symptoms in intact roots”
t0“in Arabidopsis roots”
Claim · model-written summary
Exogenous ascorbate did not activate calcium influx currents in patch-clamped root protoplasts.
- Taxon
- ArabidopsisArabidopsist0
- Organ / stage
- root protoplastse0
- Treatment
- ascorbatee1
- Outcome
- Ca2+ influx currentse0
- Direction
- does not activatee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“it does not activate Ca2+ influx currents in patch-clamped root protoplasts”
t0“in Arabidopsis roots”
e1“Exogenous ascorbate also induces a moderate increase in programmed cell death symptoms in intact roots”
Claim · model-written summary
Replacing gluconate with ascorbate revealed a large ascorbate efflux current.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- ascorbatee0
- Outcome
- ascorbate efflux currente0
- Direction
- largee0
- Comparator
- gluconatee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the replacement of gluconate with ascorbate in the patch-clamp pipette reveals a large ascorbate efflux current”
t0“in Arabidopsis roots”
Claim · model-written summary
The ascorbate efflux current was sensitive to anthracene-9-carboxylic acid.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- anthracene-9-carboxylic acid (A9C)e0
- Outcome
- sensitivitye0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“which shows sensitivity to the anion channel blocker, anthracene-9-carboxylic acid (A9C)”
t0“in Arabidopsis roots”
Claim · model-written summary
Salinity triggered accumulation of root apoplastic ascorbyl radicals in an A9C-dependent manner.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- salinity (NaCl)e0
- Outcome
- root apoplastic ascorbyl radicalse0
- Direction
- accumulatione0
- Qualifier
- A9C-dependent mannere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“salinity (NaCl) triggers the accumulation of root apoplastic ascorbyl radicals in an A9C-dependent manner”
t0“in Arabidopsis roots”
Claim · model-written summary
The authors infer that l-ascorbate leaks through anion channels under depolarization.
- Taxon
- ArabidopsisArabidopsist0
- Outcome
- l-ascorbate leaks through anion channelse0
- Qualifier
- under depolarizatione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“l-ascorbate leaks through anion channels under depolarization”
t0“in Arabidopsis roots”
The same questions in other papers
sodium chloride · molecular: metabolites · ArabidopsisPositive and negative results
1 in the opposite direction
- positive
copper atom · nutrient: content · ArabidopsisPositive and negative results
2 in the opposite direction
- negative
- negative
iron atom · nutrient: content · ArabidopsisPositive and negative results
2 papers in the same direction as this paper · 2 in the opposite direction
- negative
- no effect
- positive
1 paper more in this group
See all 5 papers →salinity · molecular: metabolites · ArabidopsisPositive and negative results
2 papers in the same direction as this paper · 10 in the opposite direction
- positive
- positive
- positive
9 papers more in this group
See all 13 papers →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.