By Helen Fosgate
For centuries people have turned to plants to cure everything from croup to heart disease. Now plants may be able to clean up after us as well.
UGA researchers have genetically engineered yellow poplar trees to give them the ability to absorb toxic mercury from soil, convert the toxin to a relatively inert form and release the converted matter as a vapor into the atmosphere. The research, the cover story in the October issue of the journal Nature Biotechnology, suggests that trees are particularly promising for phytoremediation (the use of plants--phyto--to remedy environmental pollution).
“The yellow poplar is fast-growing, has an extensive root system and large leaves that provide plenty of surface area to release processed contaminants,” says Scott Merkle, a forest biotechnologist in the Warnell School of Forest Resources. “All these make it attractive for remediation.”
Merkle and geneticists Rich Meagher, Clayton Rugh and Julie Senecoff fitted the poplars with a gene, merA, borrowed from a mercury-resistant bacteria. The bacteria are soil-borne and thrive at sites polluted with heavy metals. They also live in the guts of people with mercury amalgam fillings in their teeth. The fillings release trace amounts of mercury, “and the bacteria in our guts developed the ability to deal with this,” says Merkle.
The bacteria detoxify metals on a small scale but, alone, can’t possibly clean up the estimated $200 billion worth of heavy metal pollution in the United States. Early attempts to insert the gene in plants were only marginally successful, so researchers had to extensively modify the gene for expression in trees.
“It was Rich’s idea a dozen or more years ago to try to put this gene into plants,” says Merkle.
“It’s taken a long time, but thanks to Rich, Clayton and many others, we’ve finally got a successful, quantifiable product with the yellow poplar. And this is just one example of the many possible uses of transgenic trees.”
In laboratory trials, yellow poplars with the gene showed a 10-fold increase over control trees in their ability to absorb toxic mercury ions and convert them to a vapor. The next step, says Merkle, is to test the yellow poplars in the greenhouse and, finally, on contaminated sites in the field.
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