, Volume 226, Issue 6, pp 1379–1387 | Cite as

Enhancing tonoplast Cd/H antiport activity increases Cd, Zn, and Mn tolerance, and impacts root/shoot Cd partitioning in Nicotiana tabacum L.

  • Victor Korenkov
  • Kendal Hirschi
  • James D. Crutchfield
  • George J. Wagner
Original Article


Sequestration mechanisms that prevent high concentrations of free metal ions from persisting in metabolically active compartments of cells are thought to be central in tolerance of plants to high levels of divalent cation metals. Expression of AtCAX2 or AtCAX4, which encode divalent cation/proton antiporters, in Nicotiana tabacum cv. KY14 results in enhanced Cd- and Zn-selective transport into root tonoplast vesicles, and enhanced Cd accumulation in roots of plants exposed to moderate, 0.02 μM Cd in solution culture (Korenkov et al. in Planta 225:403–411, 2007). Here we investigated effects of expressing AtCAX2 and AtCAX4 in the same lines on tolerance to growth with near-incipient toxicity levels of Cd, Zn and Mn. Less growth inhibition (higher tolerance) to all three metals was observed in 35S::AtCAX2 and FS3::AtCAX4 expressing plants. Consistent with the tolerance observed for Cd was the finding that while root tonoplast vesicle proton pump activities of control and FS3AtCAX4 expressing plants grown in 3 μM Cd were similarly reduced, and vesicle proton leak was enhanced, root tonoplast vesicle antiporter activity of these plants remained elevated above that in controls. We suggest that CAX antiporters, unlike tonoplast proton pump and membrane integrity, are not negatively impacted by high Cd, and that supplementation of tonoplast with AtCAX compensates somewhat for reduced tonoplast proton pump and proton leak, and thereby results in sufficient vacuolar Cd sequestration to provide higher tolerance. Results are consistent with the view that CAX2 and CAX4 antiporters of tonoplast play a role in tolerance to high, toxic levels of Cd, Zn, and Mn in tobacco.


Metal tolerance Metal toxicity CAX Antiporter Membrane leakage Proton pump 



Cauliflower mosaic virus gene promoter


Sub genomic promoter from figwort mosaic virus


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Copyright information

© Springer-Verlag 2007

Authors and Affiliations

  • Victor Korenkov
    • 1
  • Kendal Hirschi
    • 2
  • James D. Crutchfield
    • 1
  • George J. Wagner
    • 1
  1. 1.Department of AgronomyUniversity of KentuckyLexingtonUSA
  2. 2.United States Department of Agriculture Research Service, Children’s Nutritional Research Center, Plant Physiology GroupBaylor College of MedicineHoustonUSA

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