Abstract
Elevations in cytoplasmic calcium ([Ca(2)+](cyt)) are an important component of early abscisic acid (ABA) signal transduction. To determine whether defined mutations in ABA signal transduction affect [Ca(2)+](cyt) signaling, the Ca(2)+-sensitive fluorescent dye fura 2 was loaded into the cytoplasm of Arabidopsis guard cells. Oscillations in [Ca(2)+](cyt) could be induced when the external calcium concentration was increased, showing viable Ca(2)+ homeostasis in these dye-loaded cells. ABA-induced [Ca(2)+](cyt) elevations in wild-type stomata were either transient or sustained, with a mean increase of approximately 300 nM. Interestingly, ABA-induced [Ca(2)+](cyt) increases were significantly reduced but not abolished in guard cells of the ABA-insensitive protein phosphatase mutants abi1 and abi2. Plasma membrane slow anion currents were activated in wild-type, abi1, and abi2 guard cell protoplasts by increasing [Ca(2)+](cyt), demonstrating that the impairment in ABA activation of anion currents in the abi1 and abi2 mutants was bypassed by increasing [Ca(2)+](cyt). Furthermore, increases in external calcium alone (which elevate [Ca(2)+](cyt)) resulted in stomatal closing to the same extent in the abi1 and abi2 mutants as in the wild type. Conversely, stomatal opening assays indicated different interactions of abi1 and abi2, with Ca(2)+-dependent signal transduction pathways controlling stomatal closing versus stomatal opening. Together, [Ca(2)+](cyt) recordings, anion current activation, and stomatal closing assays demonstrate that the abi1 and abi2 mutations impair early ABA signaling events in guard cells upstream or close to ABA-induced [Ca(2)+](cyt) elevations. These results further demonstrate that the mutations can be bypassed during anion channel activation and stomatal closing by experimental elevation of [Ca(2)+](cyt).
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Claims 10
Claim · model-written summary
External calcium induced cytoplasmic calcium oscillations.
- Taxon
- Arabidopsis
Arabidopsise1 - Treatment
- external calcium concentration was increasede0
- Outcome
- Oscillations in [Ca(2)+](cyt)e0
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Oscillations in [Ca(2)+](cyt) could be induced when the external calcium concentration was increased”
e1“Arabidopsis guard cells”
Claim · model-written summary
ABA raised cytoplasmic calcium in wild-type stomata by approximately 300 nM, transiently or sustainably.
- Taxon
- ArabidopsisArabidopsise1
- Material
- wild-typee0
- Organ / stage
- stomatae0
- Treatment
- ABAe0
- Outcome
- [Ca(2)+](cyt)e0
- Direction
- increasee0
- Value
- approximately 300 nMe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ABA-induced [Ca(2)+](cyt) elevations in wild-type stomata were either transient or sustained, with a mean increase of approximately 300 nM”
e1“Arabidopsis guard cells”
Claim · model-written summary
ABA-induced calcium increases were significantly reduced but persisted in abi1 guard cells.
- Taxon
- ArabidopsisArabidopsise1
- Material
- abi1e0
- Organ / stage
- guard cellse0
- Treatment
- ABAe0
- Outcome
- [Ca(2)+](cyt) increasese0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ABA-induced [Ca(2)+](cyt) increases were significantly reduced but not abolished in guard cells of the ABA-insensitive protein phosphatase mutants abi1 and abi2”
e1“Arabidopsis guard cells”
Claim · model-written summary
ABA-induced calcium increases were significantly reduced but persisted in abi2 guard cells.
- Taxon
- ArabidopsisArabidopsise1
- Material
- abi2e0
- Organ / stage
- guard cellse0
- Treatment
- ABAe0
- Outcome
- [Ca(2)+](cyt) increasese0
- Direction
- reducede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“ABA-induced [Ca(2)+](cyt) increases were significantly reduced but not abolished in guard cells of the ABA-insensitive protein phosphatase mutants abi1 and abi2”
e1“Arabidopsis guard cells”
Claim · model-written summary
Increasing cytoplasmic calcium activated slow anion currents in wild-type, abi1 and abi2 guard-cell protoplasts.
- Taxon
- ArabidopsisArabidopsise1
- Organ / stage
- guard cell protoplastse0
- Treatment
- increasing [Ca(2)+](cyt)e0
- Outcome
- Plasma membrane slow anion currentse0
- Direction
- activatede0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Plasma membrane slow anion currents were activated in wild-type, abi1, and abi2 guard cell protoplasts by increasing [Ca(2)+](cyt)”
e1“Arabidopsis guard cells”
Claim · model-written summary
External calcium closed stomata in abi1 to the same extent as wild type.
- Taxon
- ArabidopsisArabidopsise1
- Material
- abi1e0
- Treatment
- increases in external calcium alonee0
- Outcome
- stomatal closinge0
- Direction
- to the same extente0
- Comparator
- wild typee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increases in external calcium alone (which elevate [Ca(2)+](cyt)) resulted in stomatal closing to the same extent in the abi1 and abi2 mutants as in the wild type”
e1“Arabidopsis guard cells”
Claim · model-written summary
External calcium closed stomata in abi2 to the same extent as wild type.
- Taxon
- ArabidopsisArabidopsise1
- Material
- abi2e0
- Treatment
- increases in external calcium alonee0
- Outcome
- stomatal closinge0
- Direction
- to the same extente0
- Comparator
- wild typee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“increases in external calcium alone (which elevate [Ca(2)+](cyt)) resulted in stomatal closing to the same extent in the abi1 and abi2 mutants as in the wild type”
e1“Arabidopsis guard cells”
Claim · model-written summary
Opening assays showed different abi1 and abi2 interactions with calcium-dependent pathways controlling opening versus closing.
- Taxon
- ArabidopsisArabidopsise1
- Gene
- abi1 and abi2e0
- Outcome
- different interactions of abi1 and abi2e0
Not reportedDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“stomatal opening assays indicated different interactions of abi1 and abi2, with Ca(2)+-dependent signal transduction pathways controlling stomatal closing versus stomatal opening”
e1“Arabidopsis guard cells”
Claim · model-written summary
abi1 and abi2 mutations impair early ABA signaling upstream of or near cytoplasmic calcium elevation.
- Taxon
- ArabidopsisArabidopsise1
- Gene
- abi1 and abi2e0
- Outcome
- early ABA signaling eventse0
- Qualifier
- upstream or close to ABA-induced [Ca(2)+](cyt) elevationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“abi1 and abi2 mutations impair early ABA signaling events in guard cells upstream or close to ABA-induced [Ca(2)+](cyt) elevations”
e1“Arabidopsis guard cells”
Claim · model-written summary
Experimental cytoplasmic calcium elevation bypassed the mutations during anion-channel activation and stomatal closing.
- Taxon
- ArabidopsisArabidopsise1
- Treatment
- experimental elevation of [Ca(2)+](cyt)e0
- Gene
- abi1 and abi2e2
- Outcome
- anion channel activation and stomatal closinge0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the mutations can be bypassed during anion channel activation and stomatal closing by experimental elevation of [Ca(2)+](cyt)”
e1“Arabidopsis guard cells”
e2“abi1 and abi2 mutations”
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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.