The Arabidopsis cax1 mutant exhibits impaired ion homeostasis, development, and hormonal responses and reveals interplay among vacuolar transporters

Plant Cell. 2003 Feb;15(2):347-64. doi: 10.1105/tpc.007385.


The Arabidopsis Ca(2+)/H(+) transporter CAX1 (Cation Exchanger1) may be an important regulator of intracellular Ca(2+) levels. Here, we describe the preliminary localization of CAX1 to the tonoplast and the molecular and biochemical characterization of cax1 mutants. We show that these mutants exhibit a 50% reduction in tonoplast Ca(2+)/H(+) antiport activity, a 40% reduction in tonoplast V-type H(+)-translocating ATPase activity, a 36% increase in tonoplast Ca(2+)-ATPase activity, and increased expression of the putative vacuolar Ca(2+)/H(+) antiporters CAX3 and CAX4. Enhanced growth was displayed by the cax1 lines under Mn(2+) and Mg(2+) stress conditions. The mutants exhibited altered plant development, perturbed hormone sensitivities, and altered expression of an auxin-regulated promoter-reporter gene fusion. We propose that CAX1 regulates myriad plant processes and discuss the observed phenotypes with regard to the compensatory alterations in other transporters.

Publication types

  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Alleles
  • Antiporters / genetics
  • Antiporters / metabolism*
  • Arabidopsis / genetics
  • Arabidopsis / growth & development*
  • Arabidopsis / metabolism
  • Calcium / metabolism
  • Calcium / pharmacology
  • Calcium-Binding Proteins / genetics
  • Calcium-Binding Proteins / metabolism*
  • Cation Transport Proteins / metabolism
  • Gene Expression Regulation, Plant / drug effects
  • Homeostasis / drug effects
  • Ion Transport / drug effects
  • Mutation
  • Phenotype
  • Plant Growth Regulators / pharmacology*
  • Vacuolar Proton-Translocating ATPases / metabolism
  • Vacuoles / metabolism


  • Antiporters
  • Calcium-Binding Proteins
  • Cation Transport Proteins
  • Plant Growth Regulators
  • calcium-hydrogen antiporters
  • Vacuolar Proton-Translocating ATPases
  • Calcium