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Gene Review

CAX4  -  vacuolar cation/proton exchanger 4

Arabidopsis thaliana

Synonyms: ATCAX4, F7A7.10, F7A7_10, cation exchanger 4
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Disease relevance of CAX4

  • CAX4 driven by the CaMV 35S and FS3 [figwort mosaic virus (FMV)] promoters increased the magnitude and initial rate of Cd(2+)/H(+) exchange in root-tonoplast vesicles [1].

High impact information on CAX4

  • 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 [2].
  • We then compared the phenotypes of sCAX1- and CAX4-expressing tomato lines [3].
  • Several modifications to CAX4 allowed the protein to transport Ca(2+) [4].
  • To understand the diversity and role of H(+)/cation transporters in controlling plant ion levels, another homolog of the CAX genes, CAX4, was cloned from an Arabidopsis cDNA library [4].
  • CAX4 transcripts appeared to be expressed at low levels in all tissues and levels of CAX4 RNA increased after Mn(2+), Na(+), and Ni(2+) treatment [4].

Biological context of CAX4

  • Ion selectivity of transport in root-tonoplast vesicles isolated from FS3::CAX4-expressing plant lines having a range of gene expression was Cd(2+)>Zn(2+)>>Ca(2+)>>Mn(2+) and the ratios of maximal Cd(2+) (and Zn(2+)) versus maximal Ca(2+) and Mn(2+) transport were correlated with the levels of CAX4 expression [1].

Associations of CAX4 with chemical compounds

  • Root Cd accumulation in high CAX4 and CAX2 expressing lines was increased in seedlings grown with 0.02 muM Cd [1].


  1. Enhanced Cd(2+)-selective root-tonoplast-transport in tobaccos expressing Arabidopsis cation exchangers. Koren'kov, V., Park, S., Cheng, N.H., Sreevidya, C., Lachmansingh, J., Morris, J., Hirschi, K., Wagner, G.J. Planta (2007) [Pubmed]
  2. The Arabidopsis cax1 mutant exhibits impaired ion homeostasis, development, and hormonal responses and reveals interplay among vacuolar transporters. Cheng, N.H., Pittman, J.K., Barkla, B.J., Shigaki, T., Hirschi, K.D. Plant Cell (2003) [Pubmed]
  3. Increased calcium levels and prolonged shelf life in tomatoes expressing Arabidopsis H+/Ca2+ transporters. Park, S., Cheng, N.H., Pittman, J.K., Yoo, K.S., Park, J., Smith, R.H., Hirschi, K.D. Plant Physiol. (2005) [Pubmed]
  4. Characterization of CAX4, an Arabidopsis H(+)/cation antiporter. Cheng, N.H., Pittman, J.K., Shigaki, T., Hirschi, K.D. Plant Physiol. (2002) [Pubmed]
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