Metal-Munching Plants

Plants created to absorb metals could be used to clean up pollution

MONDAY, Dec. 31, 2001 (HealthDayNews) -- There may come a day when plants can be taught to be heavy-metal enthusiasts.

Scientists at Purdue University have identified and cloned genes believed to give a tiny mustard plant the ability to accumulate large amounts of nickel in its tissues.

This discovery could help open new avenues for scientists trying to develop plants that are able to clean up metal pollution in soil or create new food crops that provide more nutrition, says principal investigator David E. Salt, an associate professor of plant molecular physiology at Purdue.

Salt and his team identified the genes in a tiny wild mustard plant, Thlaspi goesingense, which lives in the Austrian Alps and is able to absorb large amounts of nickel. That ability is called hyperaccumulation.

The findings were published in a recent issue of the Proceedings of the National Academy of Sciences journal.

Salt and his colleagues will take the T. goesingense genes that allow for the ability to accumulate large amounts of nickel and put them into other plants that lack that ability, to see if those plants can be turned into nickel hyperaccumulators.

The first step in that effort is looking at how the genes work in a plant called Arabidopsis thaliana, a common scientific research plant. It will be a few months before Salt and his team can determine whether it's successful.

They'll then try the T. goesingense genes in other plants and, within 12 to 18 months, they should have plants ready for actual field testing, Salt says.

Leon Kochian, director of the U.S. Plant, Soil and Nutrition Laboratory at Cornell University, says the Purdue research is interesting but it remains to be seen whether it represents a breakthrough.

Kochian says Salt is one of a number of scientists studying different hyperaccumulating plants.

"That's important. I think you have to have a large tool box of genes to use for transformation of other plants to try to make them into hyperaccumulators," Kochian says.

There are about 350 different plant species known to accumulate high levels of such metals as nickel, zinc, cadmium, selenium or manganese.

There are a number of potential applications for this kind of research, Salt says.

Specially designed plants could be used to clean soil contaminated by metals. The plants would absorb the metals from the soil. This is called phytoextraction. The plants would then be harvested, incinerated and disposed in a hazardous landfill or the metals could be reclaimed from the plants, Salt says.

This discovery also could be valuable in developing crops that are naturally enriched in certain essential micronutrients, improving their nutritional value.

"A lot of staple crops for people throughout the world have been bred for yield rather than [nutritional] quality. People are now realizing a lot of these crops are actually deficient in certain essential micronutrients like iron and zinc. In fact, iron and zinc deficiency have been termed the hidden hunger in the world," Salt says.

This research could even play a role in cancer prevention by creating food plants that can hyperaccumulate selenium, a metal shown to be anti-carcinogenic, Salt says.

What to Do: Phytoextraction is just one form of phytoremediation, a term that refers to the use of plants to clean polluted sites. To learn more about the topic, go to the U.S. Environmental Protection Agency, or this site hosted by the Missouri Botanical Garden.

SOURCES: Interviews with David E. Salt, Ph.D., associate professor of plant molecular physiology, Purdue University, West Lafayette, Ind.; Leon Kochian, Ph.D., professor, department of plant biology, and director, U.S. Plant, Soil and Nutrition Laboratory, Cornell University, Ithaca, N.Y.
Consumer News