Elevated expression of TcHMA3 plays a key role in the extreme Cd tolerance in a Cd-hyperaccumulating ecotype of Thlaspi caerulescens

Daisei Ueno, Matthew J. Milner, Naoki Yamaji, Kengo Yokosho, Emi Koyama, M. Clemencia Zambrano, Molly Kaskie, Stephen Ebbs, Leon V. Kochian, Jian Feng Ma

    Research output: Contribution to journalArticlepeer-review

    160 Citations (Scopus)

    Abstract

    Summary Cadmium (Cd) is a highly toxic heavy metal for plants, but several unique Cd-hyperaccumulating plant species are able to accumulate this metal to extraordinary concentrations in the aboveground tissues without showing any toxic symptoms. However, the molecular mechanisms underlying this hypertolerance to Cd are poorly understood. Here we have isolated and functionally characterized an allelic gene, TcHMA3 (heavy metal ATPase 3) from two ecotypes (Ganges and Prayon) of Thlaspi caerulescens contrasting in Cd accumulation and tolerance. The TcHMA3 alleles from the higher (Ganges) and lower Cd-accumulating ecotype (Prayon) share 97.8% identity, and encode a P1B-type ATPase. There were no differences in the expression pattern, cell-specificity of protein localization and transport substrate-specificity of TcHMA3 between the two ecotypes. Both alleles were characterized by constitutive expression in the shoot and root, a tonoplast localization of the protein in all leaf cells and specific transport activity for Cd. The only difference between the two ecotypes was the expression level of TcHMA3: Ganges showed a sevenfold higher expression than Prayon, partly caused by a higher copy number. Furthermore, the expression level and localization of TcHMA3 were different from AtHMA3 expression in Arabidopsis. Overexpression of TcHMA3 in Arabidopsis significantly enhanced tolerance to Cd and slightly increased tolerance to Zn, but did not change Co or Pb tolerance. These results indicate that TcHMA3 is a tonoplast-localized transporter highly specific for Cd, which is responsible for sequestration of Cd into the leaf vacuoles, and that a higher expression of this gene is required for Cd hypertolerance in the Cd-hyperaccumulating ecotype of T. caerulescens.

    Original languageEnglish
    Pages (from-to)852-862
    Number of pages11
    JournalPlant Journal
    Volume66
    Issue number5
    DOIs
    Publication statusPublished - Jun 2011

    Keywords

    • cadmium
    • hyperaccumulator
    • tolerance
    • transporter
    • vacuole

    ASJC Scopus subject areas

    • Genetics
    • Plant Science
    • Cell Biology

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