Abstract
Arabidopsis thaliana has become a powerful tool in genetics and molecular biology. In order to use Arabidopsis as a model system for electrophysiological studies on plant cells, a detailed characterization of the transporters present in the plasma and vacuolar membranes of this species is required. We used the patch-clamp technique to study ion channels in the plasma membrane of Arabidopsis mesophyll cells. The most prominent conductance in these cells was a K(+)-selective, voltage-dependent, outwardly-rectifying channel (IK,out). In the whole-cell configuration, IK,out was observed in 100% of the cells assayed. In contrast, inward current was observed in less than 50% of the cells which were bathed in 100 mM K+, and was totally absent from cells bathed in 10 mM K+. The activation kinetics of IK,out were modulated by the external K+ concentration with a faster activation at low external K+. Tail-current analysis revealed that in addition to K+, IK,out is also permeable to Ca2+ and Ba2+. Externally applied Ba2+ also caused a voltage-dependent decrease in current magnitude, indicating that IK,out is also partially blocked by this classic K+ channel blocker. Single channels studied in outside-out patches showed Ca2+ and Ba2+ sensitivity, voltage dependence and time activation similar to that of IK,out in the whole-cell configuration. Given their permeability to Ca2+, these channels may function as an avenue for Ca2+ influx as well as K+ efflux, both of which may affect photosynthesis.
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Claims 9
Claim · model-written summary
The dominant mesophyll conductance was a selective voltage dependent outward K channel.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae1 - Outcome
- K(+)-selective, voltage-dependent, outwardly-rectifying channel (IK,out)e0
Not reportedOrgan / stage
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The most prominent conductance in these cells was a K(+)-selective, voltage-dependent, outwardly-rectifying channel (IK,out).”
e1“Arabidopsis thaliana”
Claim · model-written summary
IK,out occurred in all assayed cells.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Outcome
- IK,out was observede0
- Value
- 100%e0
Not reportedOrgan / stage
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“IK,out was observed in 100% of the cells assayed.”
e1“Arabidopsis thaliana”
Claim · model-written summary
Inward current appeared in fewer than half of cells at 100 mM K+.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- 100 mM K+e0
- Outcome
- inward currente0
- Value
- less than 50%e0
Not reportedOrgan / stage
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“inward current was observed in less than 50% of the cells which were bathed in 100 mM K+”
e1“Arabidopsis thaliana”
Claim · model-written summary
Inward current was absent at 10 mM K+.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- 10 mM K+e0
- Direction
- totally absente0
Not reportedOrgan / stageOutcome
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“was totally absent from cells bathed in 10 mM K+”
e1“Arabidopsis thaliana”
Claim · model-written summary
Low external K+ accelerated IK,out activation.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Compound
- external K+e0
- Outcome
- activation kinetics of IK,oute0
- Direction
- fastere0
- Qualifier
- low external K+e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The activation kinetics of IK,out were modulated by the external K+ concentration with a faster activation at low external K+.”
e1“Arabidopsis thaliana”
Claim · model-written summary
IK,out was permeable to Ca2+ and Ba2+ in addition to K+.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Compound
- K+e0
- Outcome
- IK,out is also permeable to Ca2+ and Ba2+e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in addition to K+, IK,out is also permeable to Ca2+ and Ba2+”
e1“Arabidopsis thaliana”
Claim · model-written summary
External Ba2+ caused a voltage dependent reduction in IK,out current.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Treatment
- Externally applied Ba2+e0
- Outcome
- current magnitudee0
- Direction
- decreasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Externally applied Ba2+ also caused a voltage-dependent decrease in current magnitude”
e1“Arabidopsis thaliana”
Claim · model-written summary
Outside out single channels resembled whole cell IK,out in Ca2+/Ba2+ sensitivity, voltage dependence and activation time.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Outcome
- Ca2+ and Ba2+ sensitivity, voltage dependence and time activatione0
- Comparator
- IK,out in the whole-cell configuratione0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Single channels studied in outside-out patches showed Ca2+ and Ba2+ sensitivity, voltage dependence and time activation similar to that of IK,out in the whole-cell configuration.”
e1“Arabidopsis thaliana”
Claim · model-written summary
The channels may mediate Ca2+ influx and K+ efflux, with possible effects on photosynthesis.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae1
- Outcome
- Ca2+ influx as well as K+ effluxe0
- Qualifier
- may affect photosynthesise0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“these channels may function as an avenue for Ca2+ influx as well as K+ efflux, both of which may affect photosynthesis”
e1“Arabidopsis thaliana”