Phytoremediation of mercury and organomercurials in chloroplast transgenic plants: Enhanced root uptake, translocation to shoots, and volatilization

    Authors

    S. Hussein; O. N. Ruiz; N. Terry;H. Daniell

    Comments

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    Abbreviated Journal Title

    Environ. Sci. Technol.

    Keywords

    RESISTANCE; OPERON; GENE; ACCUMULATION; CONTAINMENT; STRATEGIES; TOLERANCE; TOXICITY; SELENIUM; Engineering, Environmental; Environmental Sciences

    Abstract

    Transgenic tobacco plants engineered with bacterial merA and merB genes via the chloroplast genome were investigated to study the uptake, translocation of different forms of mercury (Hg) from roots to shoots, and their volatilization. Untransformed plants, regardless of the form of Hg supplied, reached a saturation point at 200 mu M of phenylmercuric acetate (PMA) or HgCl2, accumulating Hg concentrations up to 500 mu g g(-1) with significant reduction in growth. In contrast, chloroplast transgenic lines continued to grow well with Hg concentrations in root tissues up to 2000 mu g g(-1). Chloroplast transgenic lines accumulated both the organic and inorganic Hg forms to levels surpassing the concentrations found in the soil. The organic-Hg form was absorbed and translocated more efficiently than the inorganic-Hg form in transgenic lines, whereas no such difference was observed in untransformed plants. Chloroplast-transgenic lines showed about 100-fold increase in the efficiency of Hg accumulation in shoots compared to untransformed plants. This is the first report of such high levels of Hg accumulation in green leaves or tissues. Transgenic plants attained a maximum rate of elemental-Hg volatilization in two days when supplied with PMA and in three days when supplied with inorganic-Hg, attaining complete volatilization within a week. The combined expression of merAB via the chloroplast genome enhanced conversion of Hg2+ into Hg,(0) conferred tolerance by rapid volatilization and increased uptake of different forms of mercury, surpassing the concentrations found in the soil. These investigations provide novel insights for improvement of plant tolerance and detoxification of mercury.

    Journal Title

    Environmental Science & Technology

    Volume

    41

    Issue/Number

    24

    Publication Date

    1-1-2007

    Document Type

    Article

    Language

    English

    First Page

    8439

    Last Page

    8446

    WOS Identifier

    WOS:000251582800039

    ISSN

    0013-936X

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