Poster: Heavy metals & phytoremediation
Abs #
49: Increased arsenic hyperaccumulation in transgenic Arabidopsis by suppressing an endogenous arsenate reductase (AtACR2)
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Presenter: |
Dhankher, Om Parkash , parkash@uga.edu |
Authors | Dhankher, Om Parkash (A) Meagher, Richard B. (A) | | Affiliations: |
(A): Department of Genetics, University of Georgia, Athens GA 30602
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Arsenic is an extremely toxic metalloid pollutant that adversely affects the health of millions of people worldwide. Recently, we engineered Arabidopsis plants co-expressing the E. coli arsenate reductase (ArsC) gene in leaves and the γ-ECS (γ-glutamylcysteine synthetase) gene, constitutively. These plants showed significantly greater arsenic tolerance and accumulation than γ-ECS, ArsC alone or wild type plants (Dhankher et al., 2002, Nature Biotech. 20:1140-1145). To further enhance arsenic movement in aboveground tissues, we examined the endogenous plant activity that affects the electrochemical state and binding of arsenic in roots. The most common and oxidized form of arsenic, arsenate, is a phosphate analogue that appears to be recognized by phosphate uptake and transport systems. Arsenite is a thiol-reactive reagent that binds tightly to root tissues and is not translocated. We have proposed that by blocking the activity of endogenous plant arsenate reductase in roots and enhancing its activity in leaves, the uptake, translocation and aboveground accumulation of arsenic can be enhanced. We have identified a single gene AtACR2, in the Arabidopsis genome, with weak homology to the yeast arsenic reductase gene Acr2. AtACR2 cDNA coding sequence complements the E. coli ArsC gene functions in E. coli. Inactivating AtACR2 expression with RNAi interference results in Arabidopsis plants with a dramatic (10 to 14-fold) increase in arsenic accumulation in aboveground tissues, consistent with our model. AtACR2 encodes the first known plant arsenate reductase and has conserved homologs in many plant species. Altering the expression of these plant arsenate reductase genes should play a vital role in the phytoremediation of environmental arsenic contamination.
