Heavy Metals and Phytoremediation
Meetam, Metha , Goldsbrough, Peter .
Identification of Regulatory Components that Mediate Copper-Induced Expression of a Metallothionein Gene in Arabidopsis.
Metallothioneins (MTs) are small cysteine-rich metal-binding proteins found in most eukaryotes. Four classes of MTs are conserved in angiosperms, but their functions remain enigmatic. In Arabidopsis thaliana, RNA expression of the MT2a gene in vegetative tissues is induced by copper and oxidative stress. Deletion analysis of the MT2a promoter identified sequences from -193 to -130 upstream of the transcriptional start site that were essential for induction of the GUS reporter gene in response to Cu and H2O2. T-DNA insertion at -97 in the promoter region of the mt2a-1 mutant, but not at -215 in the promoter of mt2a-2 mutant, also abolishes Cu/H2O2-induced RNA expression of the MT2a gene. Fusion of the -201 to -126 promoter sequence from MT2a to a minimal 35S promoter rendered the chimeric promoter inducible by Cu and H2O2. These results suggest that the -193 to -130 promoter sequence is both necessary and sufficient for responsiveness to Cu and H2O2. We are currently conducting experiments to test whether two imperfect 20 bp repeats that reside within this region of the promoter serve as the Cu-responsive cis-acting elements and provide binding sites for metalloregulatory transcription factors. To identify additional trans-acting regulatory factors that may mediate copper induction of the MT2a gene, a small population of EMS-mutagenized Arabidopsis seedlings carrying MT2a::GUS was screened for mutants with altered MT2a expression and/or tolerance to copper. Preliminary characterization showed that the lrb25 mutant contained a recessive mutation leading to constitutive MT2a expression in roots and increased tolerance of roots to copper toxicity.
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1 - Purdue University, Department of Botany and Plant Pathology, Lilly Hall of Life Sciences, 915 W. State Street, West Lafayette, IN, 47907, USA
2 - Purdue University, Department of Botany and Plant Pathology
Presentation Type: Plant Biology Abstract
Location: Exhibit Hall (Northeast, Southwest & Southeast)/Hilton
Date: Sunday, July 8th, 2007
Time: 8:00 AM