By Roland Piquepaille
I'm often impressed by some scientists' ideas. But today, I'm a little bit worried, as researchers have genetically modified a common plant, the Indian mustard, to absorb more selenium, a toxic heavy metal found in soils polluted by irrigation wastewater. The transgenic plants were four times more efficient at swallowing selenium than natural ones in a contaminated area of California's Central Valley, according to articles from Nature and Wired News. These field tests are only experiments, but the researchers also want to add genes to other plants to remove different toxic materials from soils, such as mercury. What would happen if such transgenic plants filled with dangerous chemicals start to crossbreed with natural ones? Or if an insect eats these plants before being eaten itself in the natural food chain, leading to some selenium in our food? Read more and tell me what you think...Let's start with the good news from the Nature article.
Genetically modified Indian mustard plants have successfully cleaned up excessive selenium in a California field. This is the first field trial for a pollution-busting transgenic plant, and it proves that the technology can work outside the laboratory, say the researchers who carried out the test.
Farmland in certain parts of California is heavily irrigated, and the water dissolves selenium in shale found in the region. As the water evaporates on the surface soil, selenium is concentrated to levels that are toxic to plants. But Indian mustard (Brassica juncea) has a natural resistance to the element, and absorbs it as it takes in water through its roots.
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Here is a picture of natural Indian mustard plants growing in Kansas (Credit: Kansas Wildflowers And Grasses). |
To increase the level of absorption of selenium by the Indian mustard plants, the researchers, led by Norman Terry, a plant biologist at the University of California, Berkeley, added extra genes to the plant. And here are the first field test results.
The researchers created three different strains of the transgenic mustard plants, each producing different enzymes to soak up selenium, and tested them in selenium-contaminated soils alongside wild-type Indian mustard. [And] hey found that the transgenic plants could accumulate up to 4.3 times as much selenium as conventional, wild-type Indian mustard.
The transgenic plants showed up to 80% of the growth expected in uncontaminated soil, whereas the wild-type plants had their growth halved by the selenium. They were harvested after 45 days in the field, but the researchers expect that longer growth periods could remove more selenium, and estimate that the most effective plants removed about 4.4% of the element in the top 25 centimetres of soil.
The process known as phytoremediation, which uses natural plants to remove toxic materials from soil, is not new, and is cheaper than traditional methods, which imply to remove polluted soil some place before burying it elsewhere. But it takes a long time, so adding genes to speed the process is an attractive solution. But what about the long term ecological impact?
The possibility of the transgenic plants crossbreeding with food crops is a worry, admits Clayton Rugh, a plant biologist at Michigan State University in East Lansing. "If you're going to engineer a plant to take up high quantities of metals, you must ensure it doesn't get into food crops," he says. "They would have to be carefully contained with measures above and beyond those for genetically modified food crops," he says.
Another source mentioned by Wired News also admits there are some dangers.
"We don't know enough about the unintended effects of genetic engineering," said Gurian-Sherman, senior scientist with the Center for Food Safety. 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?
On the contrary, Terry doesn't seem concerned by the consequences of such experiments. Read carefully this quote from Nature.
In a useful spin-off, the Indian mustard plants could eventually be used as feed for cattle with insufficient selenium in their diet, says Terry. The team is now trying to boost the plants' power even more. "We'd like to see increases in accumulation of 10 to 100 times that possible with wild-type plants," says Terry. "This research is a great start."
Let me summarize this. First, you add genes to a plant which will then easily absorb dangerous and toxic chemicals. Then you use these plants to feed cows. But why on earth a cow would need to ingest more selenium? And are you sure that you want this selenium in your plate?
I'm not an expert in this field, but these experiments look quite dangerous to me in the long term, especially if they become widespread.
By the way, the research work has been published by Environmental Science & Technology on February 1, 2005. Here is a link to the abstract of the paper called "Field Trial of Transgenic Indian Mustard Plants Shows Enhanced Phytoremediation of Selenium-Contaminated Sediment."
Can we benefit from this or not? Please post your comments and tell me what you think.
Sources: Mark Peplow, Nature, February 11, 2005; Stephen Leahy, Wired News, February 12, 2005; and various websites
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Famous quotes containing the words mustard, cleans and/or soils:
“when wine redeems the sight,
Narrowing the mustard scansions of the eyes,”
—Hart Crane (1899–1932)
“There is no release
In a bodkin or disease,
Nor can there be a work so great
As that which cleans man’s dirty slate.”
—William Butler Yeats (1865–1939)
“He bends to the order of the seasons, the weather, the soils and crops, as the sails of a ship bend to the wind. He represents continuous hard labor, year in, year out, and small gains. He is a slow person, timed to Nature, and not to city watches. He takes the pace of seasons, plants and chemistry. Nature never hurries: atom by atom, little by little, she achieves her work.”
—Ralph Waldo Emerson (1803–1882)