title: Mutations in CAX1 produce phenotypes characteristic of plants tolerant to serpentine soils.
abstract: Plant tolerance of serpentine soils is potentially an excellent model for studying the genetics of adaptive variation in natural populations. A large-scale viability screen of Arabidopsis thaliana mutants on a defined nutrient solution with a low Ca(2+) : Mg(2+) ratio (1 : 24 mol : mol), typical of serpentine soils, yielded survivors with null alleles of the tonoplast calcium-proton antiporter CAX1. cax1 mutants have most of the phenotypes associated with tolerance to serpentine soils, including survival in solutions with a low Ca(2+) : Mg(2+) ratio; requirement for a high concentration of Mg(2+) for maximum growth; reduced leaf tissue concentration of Mg(2+); and poor growth performance on 'normal' levels of Ca(2+) and Mg(2+). A physiological model is proposed to explain how loss-of-function cax1 mutations could produce all these phenotypes characteristic of plants adapted to serpentine soils, why 'normal' plants are unable to survive on serpentine soil, and why serpentine-adapted plants are unable to compete on 'normal' soils.
authors.affiliation: Department of Biology, University of Washington, Seattle, WA 98195, USA. toby@u.washington.edu
authors.forename: H D
authors.initials: HD
authors.lastname: Bradshaw
mesh_terms: D000222:Adaptation, Physiological; D000483:Alleles; D017920:Antiporters / Q000235:genetics / Q000378:metabolism*; D017360:Arabidopsis / Q000235:genetics* / Q000502:physiology*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002118:Calcium / Q000032:analysis / Q000378:metabolism; D002135:Calcium-Binding Proteins / Q000235:genetics / Q000378:metabolism*; D027682:Cation Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008274:Magnesium / Q000032:analysis / Q000378:metabolism; D009154:Mutation; D010641:Phenotype; D012987:Soil / Q000032:analysis*
chemical_list: D017920:Antiporters; D029681:Arabidopsis Proteins; D002135:Calcium-Binding Proteins; D027682:Cation Transport Proteins; D012987:Soil; C027614:calcium-hydrogen antiporters; D008274:Magnesium; D002118:Calcium