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Yeast Metallothionein in Transgenic Tobacco Promotes Copper Uptake from Contaminated Soils

Authors

  • John C. Thomas,

    Corresponding author
    1. Biological Sciences, Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Rd., Dearborn, Michigan 48128–1491
    • Biological Sciences, Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Rd., Dearborn, Michigan 48128–1491. Phone: (313) 593–5326. Fax: (313) 593–4937
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  • Elizabeth C. Davies,

    1. Biological Sciences, Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Rd., Dearborn, Michigan 48128–1491
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  • Farah K. Malick,

    1. Biological Sciences, Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Rd., Dearborn, Michigan 48128–1491
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  • Charles Endreszl,

    1. Biological Sciences, Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Rd., Dearborn, Michigan 48128–1491
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  • Chandra R. Williams,

    1. Biological Sciences, Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Rd., Dearborn, Michigan 48128–1491
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  • Mohammed Abbas,

    1. Biological Sciences, Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Rd., Dearborn, Michigan 48128–1491
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  • Sally Petrella,

    1. Biological Sciences, Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Rd., Dearborn, Michigan 48128–1491
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  • Krystal Swisher,

    1. Environmental Sciences, Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Rd., Dearborn, Michigan 48128–1491
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  • Mike Perron,

    1. Biological Sciences, Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Rd., Dearborn, Michigan 48128–1491
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  • Ryan Edwards,

    1. Biological Sciences, Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Rd., Dearborn, Michigan 48128–1491
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  • Pam Ostenkowski,

    1. Biological Sciences, Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Rd., Dearborn, Michigan 48128–1491
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  • Nicolas Urbanczyk,

    1. Biological Sciences, Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Rd., Dearborn, Michigan 48128–1491
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  • Wendy N. Wiesend,

    1. Biological Sciences, Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Rd., Dearborn, Michigan 48128–1491
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  • Kent S. Murray

    1. Environmental Sciences, Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Rd., Dearborn, Michigan 48128–1491
    2. Geology Sciences, Department of Natural Sciences, University of Michigan-Dearborn, 4901 Evergreen Rd., Dearborn, Michigan 48128–1491
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Abstract

Metallothioneins (MTs) are metal-binding proteins that confer heavy metal tolerance and accumulation in yeast. To augment higher plant metal sequestration, the yeast metallothionein (CUP 1) was introduced into tobacco plants. The CUP 1 gene expression and copper and cadmium phytoextraction were determined. To confirm transformation, selfed and kanamycin-resistant third generation plants were subjected to DNA blot and polymerase chain reaction (PCR) analysis. A 4 mM CuSO4 stress for 7 days resulted in a decline in CUP 1 transcripts versus nonstress conditions. Despite low mRNA levels, CUP 1 transformants accumulated up to seven times more copper in older versus younger leaves during copper stress. Pooled leaves of transgenic plants grown in soils from copper stamp-sands contained two to three times the copper content as that of the control plants. Unlike some previous reports featuring MT overexpression in plants, CUP 1 seedlings did not significantly sequester or demonstrate tolerance to CdCl2. Using this transgenic approach, yeast CUP 1 expression under nonstressed conditions contributed to copper metal phytoextraction during a subsequent copper challenge. This strategy could be incorporated into plants designed for enhanced phytoremediation of metal contaminants.

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