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Genetically modified plants may be the green solution for cleaning up contaminated soils. The results of a successful field trial in California last year were published last week in the online arm of Environmental Science & Technology. They showed that genetic engineering boosted a plant's ability to absorb selenium, a toxic heavy metal, by 430 percent. "It was our first trial, and we were surprised at how well it worked," said study author Norman Terry, a professor of plant and microbial biology with the University of California, Berkeley. Phytoremediation -- the use of plants to absorb or break down contaminants -- has been used over the past decade with varying success. Genetic engineering offers the potential to ramp up the slow-growing phytoremediation industry with a new generation of toxin-cleaning super plants. Terry chose Indian mustard, a fast-growing plant with natural abilities to tolerate toxic soils. He genetically enhanced the plant's ability to convert selenium into a nontoxic form. That allowed the plants to accumulate more of the contaminant without being killed. The test plants were grown outside in heavily contaminated soils taken from the San Luis Drain, a concrete-lined canal that was used to channel irrigation wastewater from Central Valley farms until the pollution starting killing birds. In conditions that would kill other plants, the genetically modified mustard thrived, doing nearly as well as the non-modified control plants in normal soil, Terry said. Selenium contamination is a serious problem in California's Central Valley and other farmlands in the West that use irrigation water. As it evaporates, low levels of selenium in the water build up in the soil year after year. Selenium is considered an essential trace mineral for both humans and animals, but it becomes toxic at high doses. As much as 2.6 million acres of Western agricultural land are considered susceptible to selenium contamination, according to a U.S. Department of the Interior study (.pdf). "Phytoremediation is very cheap compared to bulldozing the soil and carting it off for landfill or to some decontamination facility," said Terry. His success so far is just a "proof of concept" and not good enough to consider commercially. The next step is to turn the mustard into a super-duper selenium vacuum and magnify its absorption abilities 100-fold. Terry thinks he may already have the solution. Instead of engineering the plant to absorb more selenium, he plans to enable the Indian mustard to transform selenium into a harmless gas and release it from the leaves. "We've been able to do it with plants in the lab," he said. An application to grow the new plants outside is before the U.S. Department of Agriculture, but obtaining permission is "very difficult," he said. That's as it should be, said Doug Gurian-Sherman, senior scientist with the Center for Food Safety. "We don't know enough about the unintended effects of genetic engineering," said Gurian-Sherman. The toxicity of plants can change, or a modified plant could interbreed with wild plants, he said. "What happens when an insect eats one of these plants, and then something else eats that insect? "Just because GM plants could be used in phytoremediation doesn't absolve them from careful safety assessments," said Gurian-Sherman. Selenium isn't the only target. Applied PhytoGenetics is working on cottonwood trees with a bacterial gene that will allow them to absorb mercury from contaminated sites and release a less-harmful form into the atmosphere. Mercury is a potent neurotoxin, often found in sediments of water bodies. The company chose water-loving cottonwoods because they grow fast. Field trials have been under way for less than two years, and, while the process seems to be working, researchers don't yet know how much mercury is being removed from the soil at the test site, said CEO David Glass. Putting mercury back into the air isn't a long-term solution, said Glass. "We're hopeful we'll develop a plant that will hold onto the mercury." But that's many years away, making it difficult to attract investors, he said. "It's too early to know how big a market this product will have," said Glass. "However, there's a growing problem (mercury contamination) out there that needs to be fixed." xponent Boostertrees Maru rob _______________________________________________ http://www.mccmedia.com/mailman/listinfo/brin-l
