A paper detailing the discovery appears this week in an advance online publication of the Proceedings of the National Academy of Sciences and will appear in the journal's August 19th issue.
Bioremediation, the process of using organisms to restore toxic or damaged areas, could substantially reduce the costs of cleaning up the nation's Superfund sites, estimated to require more than $700-billion. Of the top six pollutants at U.S. Superfund sites, four are heavy metals-lead, arsenic, mercury and cadmium-that may be able to be extracted with the help of plants.
"There are about four important steps in developing plants for bioremediation," says Julian Schroeder, a professor of biology at UCSD who headed the study. "The roots of the plant need to secrete a substance that makes the metals in the soil soluble, making it possible for the plant to take them up. The plant needs to detoxify the metals once it takes them up, and the metals need to be transported to the stems and leaves of the plant, and stored there. We have found that phytochelatins, chemicals produced by an enzyme for which our lab co-discovered the gene four years ago, unexpectedly function in the root to leaf transfer of metals."
Prior to his team's recent discovery, plant biologists presumed that phytochelatins only acted within individual plant cells, surrounding and binding to, or "chelating" heavy metal ions, forming a complex, which is then sequestered in vacuoles--large storage compartments within plant cells. Phytochelatins, in other words, were not known to travel significant distances within a plant.
If the phy
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Contact: Sherry Seethaler
sseethaler@ucsd.edu
858-534-4656
University of California - San Diego
8-Aug-2003