Poster: Heavy metals & phytoremediation
Abs #
47: Chloroplast genetic engineering facilitates phytoremediation studies and capabilities
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Presenter: |
Ruiz, Oscar N, oruiz@mail.ucf.edu |
Authors | Ruiz, Oscar N (A) Hussein, Hussein S (B) Terry, Norman (B) Daniell, Henry (A) | | Affiliations: |
(A): University of Central Florida
(B): University of California at Berkeley
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Mercury (Hg) is highly toxic and bacteria biomagnifies its toxicity when converted to methyl-Hg. A novel phytoremediation approach via chloroplast genetic engineering was achieved by integrating the native bacterial merA and merB genes which code for mercuric ion reductase and organomercurial lyase respectively into the chloroplast genome in a single transformation event. Stable integration of the merAB operon into the chloroplast genome was confirmed by PCR and Southern blot analyses. Expression of the mer operon resulted in high levels of tolerance to organomercurial compound, phenylmercuric acetate (PMA) when grown in soil containing up to 400 μm PMA. Northern-blot analyses revealed stable transcripts independently of the presence or absence of a 3’ untranslated region. Chloroplast transgenic lines showed 80% increase in dry weight over wild type (WT) plants when treated with 300 μM PMA, achieving higher dry weight and increasing root length at every concentration tested with either PMA or HgCl2. Transgenic lines were able to accumulate very high concentrations of Hg in roots (up to thousands of ppm). Total Hg accumulation in transgenic lines was 332 μg/g compared to 71 μg/g in WT, and accumulation in the plant shoot was 90-100 fold more than in WT. Transgenic lines treated with 100 μM PMA completely volatilized Hg[0] at a rate of 6.5 μg Hg volatilized g-1 dry weight d-1, removing all available PMA by day 5. Chloroplast transgenic plants were able to uptake and translocate large quantities of Hg, enabling high rates of Hg phytoremediation. For the first time, we show Hg transport to shoots. The work presented here should facilitate studies on the mechanism of Hg uptake/translocation and increase our understanding of phytoremediation.
