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[BEIJING] Chinese researchers have genetically modified tobacco and a species of algae to remove toxic heavy metals such as mercury from soil and water.

As a cheap and effective way of eliminating heavy metal pollution from the environment, the GM plants carry substantial health and economic benefits, says their developer, Ru Binggen of the Peking University's College of Life, Beijing.

Ru announced his invention in Beijing on 9 October at an international conference focusing on metallothionein, a protein produced in the livers of people and other mammals that binds easily to heavy metals.

By inserting a rat gene into tobacco and the algae, Ru's team made the plants produce metallothionein.

The genetically modified (GM) tobacco produces the protein in its roots and can absorb several hundred times more heavy metal ions from soil than normal tobacco, says Ru. The plants can then be burnt and the heavy metals safely removed from the ash.

Under trial conditions, the tobacco plants died before they could reproduce, so had to be replaced with new plants. Even so, says Ru, the method is still much cheaper than using a chemical process to remove heavy metal pollution.

A different method was used with the GM algae. Ru's team pasted the algae to a nylon membrane, which was then lowered into polluted water. After absorbing the heavy metals, the algae-covered membranes were taken out of the water and the heavy metals were extracted from them in the safety of a laboratory.

"The problem of heavy metal pollution has plagued the export of rice and vegetables from China, but our methods, if widely used, offer an economical solution to the problem," Ru told SciDev.Net.

He added, "Theoretically, the same kind of gene could be transplanted into rice to create a GM variety that will absorb heavy metals. In rice, heavy metals normally remain in the plants' roots and would not migrate to the grain."

The team's research has not yet been approved by the Chinese government for field testing but Ru said the technologies had proven effective in laboratory tests.

Ru accepts that there is still debate over whether metallothionein affects human and animal health. He says his team's research has not yet considered safety aspects of using the plants, but will do so if they get more funding.

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