Development of transgenic hybrid sweetgum (Liquidambar styraciflua × L. formosana) expressing γ-glutamylcysteine synthetase or mercuric reductase for phytoremediation of mercury pollution
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Using Agrobacterium-mediated gene transfer, we generated transgenic hybrid sweetgum (Liquidambar styraciflua × L. formosana) overexpressing two types of genes to enhance plant remediation of mercury-contaminated soil and water: bacterial γ-glutamylcysteine synthetase gene (ECS), the first and most important enzyme in phytochelatin synthesis, or various genes encoding a mercuric ion reductase (merA9, merA18, merA77). Hybrid sweetgum proembryogenic masses (PEMs) constitutively overexpressing ECS were able to grow in the presence of 50 μM HgCl2, which inhibited wild-type PEMs, but plantlets regenerated from the PEMs had abnormal form and did not survive for more than a few weeks following germination. In contrast, mature somatic embryos generated from PEMs constitutively overexpressing merA9 and merA18 converted to normal plantlets on germination medium containing 25 μM HgCl2, while control embryos were killed on 25 μM Hg(II)-medium. Transgenic merA plantlets displayed enhanced resistance to Hg(II) and released Hg(0) two to three times more efficiently than the wild-type plantlets.
KeywordsPhytoremediation Mercury Liquidambar styraciflua × L. formosana Transgenic
This research was supported in part by the Consortium for Plant Biotechnology Research, Inc. by DOE Prime Agreement No. DE-FC05-92OR22072. This support does not constitute an endorsement by DOE or by the Consortium for Plant Biotechnology Research, Inc. of the views expressed in this publication. We thank Dr. Daniel Carraway (International Paper Co.) for sharing his protocol for sweetgum transformation, Dr. Yujing Li, Dr. Joe Nairn and Dr. Andrew Heaton for advice, and Mandy Beggs, Lihua Wang, Amparo Lima and Xiuqin Xia for technical assistance.
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