Abstract
The way calcium (Ca) is stored in plants impacts upon plant, human and animal nutrition. An X-ray microanalysis study of over 40 angiosperm species has highlighted conserved accumulation patterns for Ca across different plant families; Ca is often stored in specific leaf cell-types. For instance, in grass monocots Ca accumulation occurs within vacuoles of epidermal cells whereas in the majority of eudicots Ca is predominantly stored within mesophyll cell vacuoles. To correlate gene expression with Ca accumulation profiles we micropipetted RNA from epidermal and mesophyll cells of the eudicot Arabidopsis thaliana. Cell specific RNA libraries were analysed by microarray and qPCR revealing a number of candidate membrane transporters with greater relative expression in the Ca-rich mesophyll. Knockout mutagenesis of one candidate AtCAX1, a tonoplast-localized Ca2+/H+-antiporter, resulted in no mutant phenotype. When the expression of AtCAX3, a complementing family member was also abolished, this resulted in a reduction in total leaf [Ca] and perturbance of the Ca distribution pattern. The double knockout plant had a 3-fold higher apoplastic [Ca] which correlated with reduced stomatal conductance, photosynthetic rate and consequently growth. Apoplastic [Ca], stomatal conductance and growth rate could be recovered to wild-type levels by reducing [Ca] in the growth medium. We implicate CAX1 and its homologues as major regulators of Ca distribution and apoplastic [Ca] in leaves within and between plant orders. Such information will be helpful for the manipulation of Ca within specific cell types of leafy vegetables as a tool for improving human and animal nutrition.
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Claims 10
Claim · model-written summary
Calcium accumulated in grass epidermal cell vacuoles.
Verbatim
e0“in grass monocots Ca accumulation occurs within vacuoles of epidermal cells”
Claim · model-written summary
Calcium predominantly accumulated in eudicot mesophyll cell vacuoles.
- Taxon
- eudicotseudicotyledonse0
- Organ / stage
- mesophyll cell vacuolese0
- Outcome
- Cae0
- Direction
- predominantly storede0
Verbatim
e0“in the majority of eudicots Ca is predominantly stored within mesophyll cell vacuoles”
Claim · model-written summary
Several candidate membrane transporters were more highly expressed in calcium-rich Arabidopsis mesophyll.
- Taxon
- Arabidopsis
Arabidopsist0 - Organ / stage
- mesophylle0
- Gene
- candidate membrane transporterse0
- Outcome
- relative expressione0
- Direction
- greatere0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“revealing a number of candidate membrane transporters with greater relative expression in the Ca-rich mesophyll”
t0“Arabidopsis Mesophyll Cells”
Claim · model-written summary
AtCAX1 knockout alone produced no mutant phenotype.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- Knockout mutagenesise0
- Gene
- AtCAX1e0
- Outcome
- mutant phenotypee0
- Direction
- noe0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Knockout mutagenesis of one candidate AtCAX1, a tonoplast-localized Ca2+/H+-antiporter, resulted in no mutant phenotype”
t0“Arabidopsis”
Claim · model-written summary
Abolishing both AtCAX1 and AtCAX3 reduced total leaf calcium.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- expression of AtCAX3, a complementing family member was also abolishede0
- Gene
- AtCAX3e0
- Outcome
- total leaf [Ca]e0
- Direction
- reductione0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When the expression of AtCAX3, a complementing family member was also abolished, this resulted in a reduction in total leaf [Ca]”
t0“Arabidopsis”
Claim · model-written summary
Abolishing both AtCAX1 and AtCAX3 perturbed calcium distribution.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- expression of AtCAX3, a complementing family member was also abolishede0
- Gene
- AtCAX3e0
- Outcome
- Ca distribution patterne0
- Direction
- perturbancee0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“When the expression of AtCAX3, a complementing family member was also abolished, this resulted in a reduction in total leaf [Ca] and perturbance of the Ca distribution pattern”
t0“Arabidopsis”
Claim · model-written summary
The double knockout had threefold higher apoplastic calcium.
- Taxon
- ArabidopsisArabidopsist0
- Material
- double knockout plante0
- Outcome
- apoplastic [Ca]e0
- Direction
- highere0
- Value
- 3-folde0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The double knockout plant had a 3-fold higher apoplastic [Ca]”
t0“Arabidopsis”
Claim · model-written summary
Higher apoplastic calcium correlated with reduced stomatal conductance, photosynthetic rate and growth in the double knockout.
- Taxon
- ArabidopsisArabidopsist0
- Material
- double knockout plante0
- Compound
- apoplastic [Ca]e0
- Outcome
- stomatal conductance, photosynthetic rate and consequently growthe0
- Direction
- reducede0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“The double knockout plant had a 3-fold higher apoplastic [Ca] which correlated with reduced stomatal conductance, photosynthetic rate and consequently growth”
t0“Arabidopsis”
Claim · model-written summary
Reducing calcium in the growth medium restored apoplastic calcium, stomatal conductance and growth to wild-type levels.
- Taxon
- ArabidopsisArabidopsist0
- Treatment
- reducing [Ca] in the growth mediume0
- Outcome
- Apoplastic [Ca], stomatal conductance and growth ratee0
- Direction
- recoverede0
- Comparator
- wild-type levelse0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Apoplastic [Ca], stomatal conductance and growth rate could be recovered to wild-type levels by reducing [Ca] in the growth medium”
t0“Arabidopsis”
Claim · model-written summary
The authors implicate CAX1 and homologues as regulators of leaf calcium distribution and apoplastic calcium.
- Taxon
- ArabidopsisArabidopsist0
- Organ / stage
- leavese0
- Gene
- CAX1 and its homologuese0
- Outcome
- Ca distribution and apoplastic [Ca]e0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“We implicate CAX1 and its homologues as major regulators of Ca distribution and apoplastic [Ca] in leaves within and between plant orders”
t0“Arabidopsis”
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