title: CATION EXCHANGER1 Cosegregates with Cadmium Tolerance in the Metal Hyperaccumulator Arabidopsis halleri and Plays a Role in Limiting Oxidative Stress in Arabidopsis Spp.
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.
authors.affiliation: Laboratory of Plant Physiology and Molecular Genetics, Université Libre de Bruxelles, 1050 Brussels, Belgium (C.B., C.-L.M., P.S., N.V.); andLaboratoire Evolution, Ecologie, Paléontologie, Unité Mixte de Recherche Centre National de la Recherche Scientifique 8016, F-59655 Villeneuve d'Ascq cedex, France (P.S.-L.).
authors.forename: Cecilia
authors.initials: C
authors.lastname: Baliardini
authors.affiliation: Laboratory of Plant Physiology and Molecular Genetics, Université Libre de Bruxelles, 1050 Brussels, Belgium (C.B., C.-L.M., P.S., N.V.); andLaboratoire Evolution, Ecologie, Paléontologie, Unité Mixte de Recherche Centre National de la Recherche Scientifique 8016, F-59655 Villeneuve d'Ascq cedex, France (P.S.-L.).
authors.forename: Claire-Lise
authors.initials: CL
authors.lastname: Meyer
authors.affiliation: Laboratory of Plant Physiology and Molecular Genetics, Université Libre de Bruxelles, 1050 Brussels, Belgium (C.B., C.-L.M., P.S., N.V.); andLaboratoire Evolution, Ecologie, Paléontologie, Unité Mixte de Recherche Centre National de la Recherche Scientifique 8016, F-59655 Villeneuve d'Ascq cedex, France (P.S.-L.).
authors.forename: Pietrino
authors.initials: P
authors.lastname: Salis
authors.affiliation: Laboratory of Plant Physiology and Molecular Genetics, Université Libre de Bruxelles, 1050 Brussels, Belgium (C.B., C.-L.M., P.S., N.V.); andLaboratoire Evolution, Ecologie, Paléontologie, Unité Mixte de Recherche Centre National de la Recherche Scientifique 8016, F-59655 Villeneuve d'Ascq cedex, France (P.S.-L.).
authors.forename: Pierre
authors.initials: P
authors.lastname: Saumitou-Laprade
authors.affiliation: Laboratory of Plant Physiology and Molecular Genetics, Université Libre de Bruxelles, 1050 Brussels, Belgium (C.B., C.-L.M., P.S., N.V.); andLaboratoire Evolution, Ecologie, Paléontologie, Unité Mixte de Recherche Centre National de la Recherche Scientifique 8016, F-59655 Villeneuve d'Ascq cedex, France (P.S.-L.) nverbru@ulb.ac.be.
authors.forename: Nathalie
authors.identifier: http://orcid.org/0000-0003-2296-5404
authors.initials: N
authors.lastname: Verbruggen
mesh_terms: D000222:Adaptation, Physiological / Q000187:drug effects*; D017360:Arabidopsis / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002104:Cadmium / Q000633:toxicity*; D002118:Calcium / Q000494:pharmacology; D020090:Chromosome Segregation; D003001:Cloning, Molecular; D003198:Computer Simulation; D018628:Gene Dosage; D018506:Gene Expression Regulation, Plant / Q000187:drug effects; D017343:Genes, Plant; D056726:Genetic Association Studies; D005819:Genetic Markers; D006861:Hydrogen Peroxide / Q000378:metabolism; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D018384:Oxidative Stress / Q000187:drug effects*; D040641:Quantitative Trait Loci
chemical_list: D029681:Arabidopsis Proteins; D005819:Genetic Markers; D002104:Cadmium; D006861:Hydrogen Peroxide; D002118:Calcium