Abstract
In tip-growing cells, the tip-high Ca(2+) gradient is thought to regulate the activity of components of the growth machinery, including the cytoskeleton, Ca(2+)-dependent regulatory proteins, and the secretory apparatus. In pollen tubes, both the Ca(2+) gradient and cell elongation show oscillatory behavior, reinforcing the link between the two. We report that in growing root hairs of Arabidopsis (Arabidopsis thaliana), an oscillating tip-focused Ca(2+) gradient can be resolved through imaging of a cytosolically expressed Yellow Cameleon 3.6 fluorescence resonance energy transfer-based Ca(2+) sensor. Both elongation of the root hairs and the associated tip-focused Ca(2+) gradient show a similar dynamic character, oscillating with a frequency of 2 to 4 min(-1). Cross-correlation analysis indicates that the Ca(2+) oscillations lag the growth oscillations by 5.3 +/- 0.3 s. However, growth never completely stops, even during the slow cycle of an oscillation, and the concomitant tip Ca(2+) level is always slightly elevated compared with the resting Ca(2+) concentration along the distal shaft, behind the growing tip. Artificially increasing Ca(2+) using the Ca(2+) ionophore A23187 leads to immediate cessation of elongation and thickening of the apical cell wall. In contrast, dissipating the Ca(2+) gradient using either the Ca(2+) channel blocker La(3+) or the Ca(2+) chelator EGTA is accompanied by an increase in the rate of cell expansion and eventual bursting of the root hair tip. These observations are consistent with a model in which the maximal oscillatory increase in cytosolic Ca(2+) is triggered by cell expansion associated with tip growth and plays a role in the subsequent restriction of growth.
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Claims 10
Claim · model-written summary
Growing Arabidopsis root hairs had a resolvable oscillating tip-focused calcium gradient.
- Taxon
- Arabidopsis
Arabidopsise0 - Organ / stage
- root hairse0
- Outcome
- oscillating tip-focused Ca(2+) gradiente0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“in growing root hairs of Arabidopsis (Arabidopsis thaliana), an oscillating tip-focused Ca(2+) gradient can be resolved through imaging of a cytosolically expressed Yellow Cameleon 3.6 fluorescence resonance energy transfer-based Ca(2+) sensor”
Claim · model-written summary
Root-hair elongation and calcium-gradient oscillations shared a frequency of 2 to 4 min(-1).
- Taxon
- ArabidopsisArabidopsise1
- Organ / stage
- root hairse0
- Outcome
- elongation of the root hairs and the associated tip-focused Ca(2+) gradiente0
- Value
- 2 to 4 min(-1)e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Both elongation of the root hairs and the associated tip-focused Ca(2+) gradient show a similar dynamic character, oscillating with a frequency of 2 to 4 min(-1)”
e1“Arabidopsis (Arabidopsis thaliana)”
Claim · model-written summary
Calcium oscillations lagged growth oscillations by 5.3 +/- 0.3 s.
- Taxon
- ArabidopsisArabidopsise1
- Outcome
- Ca(2+) oscillationse0
- Direction
- lage0
- Value
- 5.3 +/- 0.3 se0
- Comparator
- growth oscillationse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the Ca(2+) oscillations lag the growth oscillations by 5.3 +/- 0.3 s”
e1“Arabidopsis (Arabidopsis thaliana)”
Claim · model-written summary
Growth continued through the slow oscillation cycle.
- Taxon
- ArabidopsisArabidopsise1
- Organ / stage
- root hairse2
- Outcome
- growth never completely stopse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“growth never completely stops, even during the slow cycle of an oscillation”
e1“Arabidopsis (Arabidopsis thaliana)”
e2“elongation of the root hairs”
Claim · model-written summary
Tip calcium remained slightly above resting calcium in the distal shaft.
- Taxon
- ArabidopsisArabidopsise1
- Outcome
- tip Ca(2+) levele0
- Direction
- slightly elevatede0
- Comparator
- resting Ca(2+) concentration along the distal shafte0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“tip Ca(2+) level is always slightly elevated compared with the resting Ca(2+) concentration along the distal shaft”
e1“Arabidopsis (Arabidopsis thaliana)”
Claim · model-written summary
A23187-induced calcium increase immediately stopped root-hair elongation.
- Taxon
- ArabidopsisArabidopsise1
- Treatment
- Ca(2+) ionophore A23187e0
- Outcome
- elongatione0
- Direction
- cessatione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Artificially increasing Ca(2+) using the Ca(2+) ionophore A23187 leads to immediate cessation of elongation and thickening of the apical cell wall”
e1“Arabidopsis (Arabidopsis thaliana)”
Claim · model-written summary
A23187-induced calcium increase thickened the apical cell wall.
- Taxon
- ArabidopsisArabidopsise1
- Treatment
- Ca(2+) ionophore A23187e0
- Outcome
- apical cell walle0
- Direction
- thickeninge0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Artificially increasing Ca(2+) using the Ca(2+) ionophore A23187 leads to immediate cessation of elongation and thickening of the apical cell wall”
e1“Arabidopsis (Arabidopsis thaliana)”
Claim · model-written summary
La(3+) disruption of the calcium gradient increased cell expansion and eventually burst root-hair tips.
- Taxon
- ArabidopsisArabidopsise1
- Organ / stage
- root hair tipe0
- Treatment
- Ca(2+) channel blocker La(3+)e0
- Outcome
- rate of cell expansione0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“dissipating the Ca(2+) gradient using either the Ca(2+) channel blocker La(3+) or the Ca(2+) chelator EGTA is accompanied by an increase in the rate of cell expansion and eventual bursting of the root hair tip”
e1“Arabidopsis (Arabidopsis thaliana)”
Claim · model-written summary
EGTA disruption of the calcium gradient increased cell expansion and eventually burst root-hair tips.
- Taxon
- ArabidopsisArabidopsise1
- Organ / stage
- root hair tipe0
- Treatment
- Ca(2+) chelator EGTAe0
- Outcome
- rate of cell expansione0
- Direction
- increasee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“dissipating the Ca(2+) gradient using either the Ca(2+) channel blocker La(3+) or the Ca(2+) chelator EGTA is accompanied by an increase in the rate of cell expansion and eventual bursting of the root hair tip”
e1“Arabidopsis (Arabidopsis thaliana)”
Claim · model-written summary
The authors propose expansion triggers calcium increases that then constrain growth.
- Taxon
- ArabidopsisArabidopsise1
- Outcome
- restriction of growthe0
- Qualifier
- triggered by cell expansion associated with tip growthe0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“the maximal oscillatory increase in cytosolic Ca(2+) is triggered by cell expansion associated with tip growth and plays a role in the subsequent restriction of growth”
e1“Arabidopsis (Arabidopsis thaliana)”
The same questions in other papers
calcium(2+) · growth · ArabidopsisPositive and negative results
1 paper in the same direction as this paper · 3 in the opposite direction
- positive
- positive
- positive
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