Abstract
Arabidopsis halleri is a model species for the study of plant adaptation to extreme metallic conditions. In this species, cadmium (Cd) tolerance seems to be constitutive, and the mechanisms underlying the trait are still poorly understood. A previous quantitative trait loci (QTL) analysis performed on A. halleri × Arabidopsis lyrata backcross population1 identified the metal-pump gene Heavy Metal ATPase4 as the major genetic determinant for Cd tolerance. However, although necessary, Heavy Metal ATPase4 alone is not sufficient for determining this trait. After fine mapping, a gene encoding a calcium(2+)/hydrogen(+) antiporter, cation/hydrogen(+) exchanger1 (CAX1), was identified as a candidate gene for the second QTL of Cd tolerance in A. halleri. Backcross population1 individuals displaying the A. halleri allele for the CAX1 locus exhibited significantly higher CAX1 expression levels compared with the ones with the A. lyrata allele, and a positive correlation between CAX1 expression and Cd tolerance was observed. Here, we show that this QTL is conditional and that it is only detectable at low external Ca concentration. CAX1 expression in both roots and shoots was higher in A. halleri than in the close Cd-sensitive relative species A. lyrata and Arabidopsis thaliana. Moreover, CAX1 loss of function in A. thaliana led to higher Cd sensitivity at low concentration of Ca, higher sensitivity to methylviologen, and stronger accumulation of reactive oxygen species after Cd treatment. Overall, this study identifies a unique genetic determinant of Cd tolerance in the metal hyperaccumulator A. halleri and offers a new twist for the function of CAX1 in plants.
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Claims 9
Claim · model-written summary
CAX1 was identified as a candidate gene for the second Cd-tolerance QTL.
- Taxon
- A. halleri
_IMG_7443.JPG?width=60)
Arabidopsis hallerie0 - Gene
- CAX1e0
- Outcome
- candidate gene for the second QTL of Cd tolerancee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
_IMG_7443.JPG?width=500)
Verbatim
e0“cation/hydrogen(+) exchanger1 (CAX1), was identified as a candidate gene for the second QTL of Cd tolerance in A. halleri.”
Claim · model-written summary
The A. halleri CAX1 allele was associated with significantly higher CAX1 expression than the A. lyrata allele.
- Taxon
- A. halleriArabidopsis hallerie0
- Gene
- CAX1e0
- Outcome
- CAX1 expression levelse0
- Direction
- highere0
- Comparator
- A. lyrata allelee0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“Backcross population1 individuals displaying the A. halleri allele for the CAX1 locus exhibited significantly higher CAX1 expression levels compared with the ones with the A. lyrata allele”
Claim · model-written summary
CAX1 expression was positively correlated with Cd tolerance.
Not reportedTaxon
Verbatim
e0“a positive correlation between CAX1 expression and Cd tolerance was observed”
Claim · model-written summary
The Cd-tolerance QTL was detectable only at low external Ca concentration.
Not reportedTaxon
Verbatim
e0“this QTL is conditional and that it is only detectable at low external Ca concentration”
Claim · model-written summary
Root CAX1 expression was higher in A. halleri than in A. lyrata and A. thaliana.
- Taxon
- A. halleriArabidopsis hallerie0
- Organ / stage
- rootse0
- Gene
- CAX1e0
- Outcome
- CAX1 expressione0
- Direction
- highere0
- Comparator
- A. lyrata and Arabidopsis thalianae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CAX1 expression in both roots and shoots was higher in A. halleri than in the close Cd-sensitive relative species A. lyrata and Arabidopsis thaliana.”
Claim · model-written summary
Shoot CAX1 expression was higher in A. halleri than in A. lyrata and A. thaliana.
- Taxon
- A. halleriArabidopsis hallerie0
- Organ / stage
- shootse0
- Gene
- CAX1e0
- Outcome
- CAX1 expressione0
- Direction
- highere0
- Comparator
- A. lyrata and Arabidopsis thalianae0
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CAX1 expression in both roots and shoots was higher in A. halleri than in the close Cd-sensitive relative species A. lyrata and Arabidopsis thaliana.”
Claim · model-written summary
CAX1 loss of function increased Cd sensitivity in A. thaliana at low Ca concentration.
- Taxon
- A. thaliana
Arabidopsis thalianae0 - Treatment
- CAX1 loss of functione0
- Gene
- CAX1e0
- Outcome
- Cd sensitivitye0
- Direction
- highere0
- Qualifier
- low concentration of Cae0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CAX1 loss of function in A. thaliana led to higher Cd sensitivity at low concentration of Ca”
Claim · model-written summary
CAX1 loss of function increased methylviologen sensitivity in A. thaliana.
- Taxon
- A. thalianaArabidopsis thalianae0
- Treatment
- CAX1 loss of functione0
- Gene
- CAX1e0
- Outcome
- sensitivity to methylviologene0
- Direction
- highere0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CAX1 loss of function in A. thaliana led to higher Cd sensitivity at low concentration of Ca, higher sensitivity to methylviologen”
Claim · model-written summary
CAX1 loss of function increased reactive oxygen species accumulation after Cd treatment in A. thaliana.
- Taxon
- A. thalianaArabidopsis thalianae0
- Treatment
- CAX1 loss of functione0
- Gene
- CAX1e0
- Outcome
- accumulation of reactive oxygen speciese0
- Direction
- strongere0
- Qualifier
- after Cd treatmente0
Not reportedComparator
Organisms pictured · Representative pictures of the matched species, not figures from the paper.
Verbatim
e0“CAX1 loss of function in A. thaliana led to higher Cd sensitivity at low concentration of Ca, higher sensitivity to methylviologen, and stronger accumulation of reactive oxygen species after Cd treatment”
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