Two genes encoding Arabidopsis halleri MTP1 metal transport proteins co-segregate with zinc tolerance and account for high MTP1 transcript levels

Authors

  • Dörthe B. Dräger,

    1. Max Planck Institute of Molecular Plant Physiology, D-14424 Potsdam, Germany
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  • Anne-Garlonn Desbrosses-Fonrouge,

    1. Max Planck Institute of Molecular Plant Physiology, D-14424 Potsdam, Germany
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  • Christian Krach,

    1. Max Planck Institute of Molecular Plant Physiology, D-14424 Potsdam, Germany
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    • Current address: Department of Animal Physiology, Institute of Biochemistry and Biology, University of Potsdam, Villa Liegnitz, Lennéstr. 7a, 14471 Potsdam, Germany.

  • Agnes N. Chardonnens,

    1. Max Planck Institute of Molecular Plant Physiology, D-14424 Potsdam, Germany
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    • Current address: metanomics GmbH & Co. KGaA, Tegeler Weg 33, 10589 Berlin, Germany.

  • Rhonda C. Meyer,

    1. Max Planck Institute of Molecular Plant Physiology, D-14424 Potsdam, Germany
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  • Pierre Saumitou-Laprade,

    1. Laboratoire de Génétique et Evolution des Populations Végétales, UPRSA-CNRS 8016, FR-CNRS 1818, Bâtiment SN2, Université de Lille 1, F-59655 Villeneuve d'Ascq Cedex, France
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  • Ute Krämer

    Corresponding author
    1. Max Planck Institute of Molecular Plant Physiology, D-14424 Potsdam, Germany
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(fax +49 331 5678 98 357; e-mail kraemer@mpimp-golm.mpg.de).

Summary

The zinc hyperaccumulator plant Arabidopsis halleri is able to naturally accumulate 100-fold higher leaf zinc concentrations when compared with non-accumulator species such as the closely related A. lyrata and A. thaliana, without showing toxicity symptoms. A novel member of the cation diffusion facilitator (CDF) protein family, an A. halleri metal tolerance protein 1 (MTP1), and the homologous A. thaliana Zn transporter (ZAT)/AtMTP1 metal-specifically complement the zinc hypersensitivity of a Saccharomyces cerevisiae zrc1 cot1 mutant strain. A fusion of the AhMTP1 protein to green fluorescent protein (GFP) localizes to the vacuolar membrane of A. thaliana protoplasts. When compared with A. lyrata and A. thaliana, the total MTP1 transcript levels are substantially higher in the leaves and upregulated upon exposure to high zinc concentrations in the roots of A. halleri. The high MTP1 transcript levels in A. halleri can be primarily attributed to two genetically unlinked genomic AhMTP1 gene copies. The two corresponding loci co-segregate with zinc tolerance in the back-cross 1 generation of a cross between the zinc-tolerant species A. halleri and the zinc-sensitive species A. lyrata. In contrast, a third MTP1 gene in the genome of A. halleri generates only minor amounts of MTP1 transcripts and does not co-segregate with zinc tolerance. Our data suggests that zinc tolerance in A. halleri involves an expanded copy number of an ancestral MTP1 gene, encoding functional proteins that mediate the detoxification of zinc in the cell vacuole. At the transcript level, MTP1 gene copies of A. halleri are regulated differentially and in response to changes in zinc supply.

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