Title

Metallothionein expression in chloroplasts enhances mercury accumulation and phytoremediation capability

Authors

Authors

O. N. Ruiz; D. Alvarez; C. Torres; L. Roman;H. Daniell

Comments

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Abbreviated Journal Title

Plant Biotechnol. J.

Keywords

plastid genome; real-time PCR; bioremediation; genetic engineering; chelator; environmental biotechnology; TOBACCO NICOTIANA-TABACUM; TRANSGENIC CHLOROPLASTS; PLANTS; RESISTANCE; PROTEIN; GENOME; LIGHT; GENE; TRANSCRIPTION; TRANSLATION; Biotechnology & Applied Microbiology; Plant Sciences

Abstract

P>Genetic engineering to enhance mercury phytoremediation has been accomplished by expression of the merAB genes that protects the cell by converting Hg[II] into Hg[0] which volatilizes from the cell. A drawback of this approach is that toxic Hg is released back into the environment. A better phytoremediation strategy would be to accumulate mercury inside plants for subsequent retrieval. We report here the development of a transplastomic approach to express the mouse metallothionein gene (mt1) and accumulate mercury in high concentrations within plant cells. Real-time PCR analysis showed that up to 1284 copies of the mt1 gene were found per cell when compared with 1326 copies of the 16S rrn gene, thereby attaining homoplasmy. Past studies in chloroplast transformation used qualitative Southern blots to evaluate indirectly transgene copy number, whereas we used real-time PCR for the first time to establish homoplasmy and estimate transgene copy number and transcript levels. The mt1 transcript levels were very high with 183 000 copies per ng of RNA or 41% the abundance of the 16S rrn transcripts. The transplastomic lines were resistant up to 20 mu m mercury and maintained high chlorophyll content and biomass. Although the transgenic plants accumulated high concentrations of mercury in all tissues, leaves accumulated up to 106 ng, indicating active phytoremediation and translocation of mercury. Such accumulation of mercury in plant tissues facilitates proper disposal or recycling. This study reports, for the first time, the use of metallothioniens in plants for mercury phytoremediation. Chloroplast genetic engineering approach is useful to express metal-scavenging proteins for phytoremediation.

Journal Title

Plant Biotechnology Journal

Volume

9

Issue/Number

5

Publication Date

1-1-2011

Document Type

Article

Language

English

First Page

609

Last Page

617

WOS Identifier

WOS:000290392400009

ISSN

1467-7644

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