Journal Article

Overexpression of Phytochelatin Synthase in <i>Arabidopsis</i> Leads to Enhanced Arsenic Tolerance and Cadmium Hypersensitivity

Yujing Li, Om Parkash Dhankher, Laura Carreira, David Lee, Alice Chen, Julian I. Schroeder, Rebecca S. Balish and Richard B. Meagher

in Plant and Cell Physiology

Published on behalf of Japanese Society of Plant Physiologists

Volume 45, issue 12, pages 1787-1797
Published in print December 2004 | ISSN: 0032-0781
Published online December 2004 | e-ISSN: 1471-9053 | DOI: https://dx.doi.org/10.1093/pcp/pch202
Overexpression of Phytochelatin Synthase in Arabidopsis Leads to Enhanced Arsenic Tolerance and Cadmium Hypersensitivity

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Phytochelatin synthase (PCS) catalyzes the final step in the biosynthesis of phytochelatins, which are a family of cysteine-rich thiol-reactive peptides believed to play important roles in processing many thiol-reactive toxicants. A modified Arabidopsis thaliana PCS sequence (AtPCS1) was active in Escherichia coli. When AtPCS1 was overexpressed in Arabidopsis from a strong constitutive Arabidopsis actin regulatory sequence (A2), the A2::AtPCS1 plants were highly resistant to arsenic, accumulating 20–100 times more biomass on 250 and 300 µM arsenate than wild type (WT); however, they were hypersensitive to Cd(II). After exposure to cadmium and arsenic, the overall accumulation of thiol-peptides increased to 10-fold higher levels in the A2::AtPCS1 plants compared with WT, as determined by fluorescent HPLC. Whereas cadmium induced greater increases in traditional PCs (PC2, PC3, PC4), arsenic exposure resulted in the expression of many unknown thiol products. Unexpectedly, after arsenate or cadmium exposure, levels of the dipeptide substrate for PC synthesis, γ-glutamyl cysteine (γ-EC), were also dramatically increased. Despite these high thiol-peptide concentrations, there were no significant increases in concentrations of arsenic and cadmium in above-ground tissues in the AtPCS1 plants relative to WT plants. The potential for AtPCS1 overexpression to be useful in strategies for phytoremediating arsenic and to compound the negative effects of cadmium are discussed.

Keywords: Keywords: Accumulation — Arsenite — γ-Glutamylcysteine — Mono-bromobimane — Transgene.; Abbreviations: A2, cassette containing Arabidopsis actin ACT2 promoter and terminator; AtPCS, Arabidopsis phytochelatin synthase; γ-EC, γ-glutamylcysteine; GSH, glutathione; PCs, phytochelatins; PCS: phytochelatin synthase.

Journal Article.  6996 words.  Illustrated.

Subjects: Biochemistry ; Molecular and Cell Biology ; Plant Sciences and Forestry

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