Abstract
A transient increase in cytosolic Ca2+ concentration ([Ca2+]cyt) is thought to be a prerequisite for an appropriate physiological response to both chilling and salt stress. The [Ca2+]cyt is raised by Ca2+ influx to the cytosol from the apoplast and/or intracellular stores. It has been speculated that different signals mobilise Ca2+ from different stores, but little is known about the origin(s) of the Ca2+ entering the cytosol in response to specific environmental challenges. We have utilised the developmentally regulated suberisation of endodermal cells, which is thought to prevent Ca2+ influx from the apoplast, to ascertain whether Ca2+ influx is required to increase [Ca2+]cyt in response to chilling or salt stress. Perturbations in [Ca2+]cyt were studied in transgenic Arabidopsis thaliana, expressing aequorin fused to a modified yellow fluorescent protein solely in root endodermal cells, during slow cooling of plants from 20 to 0.5 degrees C over 5 min and in response to an acute salt stress (0.333 m NaCl). Only in endodermal cells in the apical 4 mm of the Arabidopsis root did [Ca2+]cyt increase significantly during cooling, and the magnitude of the [Ca2+]cyt elevation elicited by cooling was inversely related to the extent of suberisation of the endodermal cell layer. No [Ca2+]cyt elevations were elicited by cooling in suberised endodermal cells. This is consistent with the hypothesis that suberin lamellae isolate the endodermal cell protoplast from the apoplast and, thereby, prevent Ca2+ influx. By contrast, acute salt stress increased [Ca2+]cyt in endodermal cells throughout the root. These results suggest that [Ca2+]cyt elevations, upon slow cooling, depend absolutely on Ca2+ influx across the plasma membrane, but [Ca2+]cyt elevations in response to acute salt stress do not. They also suggest that Ca2+ release from intracellular stores contributes significantly to increasing [Ca2+]cyt upon acute salt stress.
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Claims 7
Claim · model-written summary
Cytosolic Ca2+ increased significantly during slow cooling only in endodermal cells of the apical 4 mm of the Arabidopsis root.
- Taxon
- Arabidopsis thaliana
Arabidopsis thalianae0 - Organ / stage
- endodermal cells in the apical 4 mm of the Arabidopsis roote1
- Treatment
- slow cooling of plants from 20 to 0.5 degrees C over 5 mine2
- Outcome
- [Ca2+]cyte1
- Direction
- increasee1
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“transgenic Arabidopsis thaliana”
e1“Only in endodermal cells in the apical 4 mm of the Arabidopsis root did [Ca2+]cyt increase significantly during cooling”
e2“slow cooling of plants from 20 to 0.5 degrees C over 5 min”
Claim · model-written summary
The magnitude of the cooling-induced cytosolic Ca2+ elevation was inversely related to the extent of endodermal suberisation.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Treatment
- extent of suberisation of the endodermal cell layere3
- Outcome
- magnitude of the [Ca2+]cyt elevation elicited by coolinge3
- Direction
- decreaseinferrede3
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“transgenic Arabidopsis thaliana”
e3“the magnitude of the [Ca2+]cyt elevation elicited by cooling was inversely related to the extent of suberisation of the endodermal cell layer”
Claim · model-written summary
Cooling did not elicit cytosolic Ca2+ elevations in suberised endodermal cells.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Organ / stage
- suberised endodermal cellse4
- Treatment
- coolinge4
- Outcome
- [Ca2+]cyt elevationse4
Not reportedComparatorDirection
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“transgenic Arabidopsis thaliana”
e4“No [Ca2+]cyt elevations were elicited by cooling in suberised endodermal cells”
Claim · model-written summary
Acute salt stress increased cytosolic Ca2+ in endodermal cells throughout the root.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Organ / stage
- endodermal cells throughout the roote6
- Treatment
- acute salt stresse6
- Outcome
- [Ca2+]cyte6
- Direction
- increasede6
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“transgenic Arabidopsis thaliana”
e6“acute salt stress increased [Ca2+]cyt in endodermal cells throughout the root”
Claim · model-written summary
Suberin lamellae probably isolate the endodermal protoplast from the apoplast and so prevent Ca2+ influx.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Outcome
- Ca2+ influxe5
- Qualifier
- suberin lamellae isolate the endodermal cell protoplast from the apoplaste5
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“transgenic Arabidopsis thaliana”
e5“This is consistent with the hypothesis that suberin lamellae isolate the endodermal cell protoplast from the apoplast and, thereby, prevent Ca2+ influx”
Claim · model-written summary
Cooling-induced cytosolic Ca2+ elevations depend absolutely on Ca2+ influx across the plasma membrane.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Outcome
- [Ca2+]cyt elevationse7
- Qualifier
- depend absolutely on Ca2+ influx across the plasma membranee7
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“transgenic Arabidopsis thaliana”
e7“These results suggest that [Ca2+]cyt elevations, upon slow cooling, depend absolutely on Ca2+ influx across the plasma membrane”
Claim · model-written summary
Ca2+ release from intracellular stores contributes significantly to the salt-stress increase in cytosolic Ca2+.
- Taxon
- Arabidopsis thalianaArabidopsis thalianae0
- Treatment
- acute salt stresse1
- Outcome
- increasing [Ca2+]cyte1
- Qualifier
- Ca2+ release from intracellular storese1
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“transgenic Arabidopsis thaliana”
e1“Ca2+ release from intracellular stores contributes significantly to increasing [Ca2+]cyt upon acute salt stress”