Mutated plants may help clean soil

A plant with a mutation in a gene called MDHAR6 (right) shows enhanced tolerance to TNT in the soil compared with a plant without the mutation (left). The pollutant has become highly prevalent in soil in the last century.
A plant with a mutation in a gene called MDHAR6 (right) shows enhanced tolerance to TNT in the soil compared with a plant without the mutation (left). The pollutant has become highly prevalent in soil in the last century.PHOTO: REUTERS

WASHINGTON • Scientists have identified a mutation in plants that allows them to break down TNT, raising the possibility of a new approach to cleaning up land contaminated by the commonly used explosive.

TNT, or 2,4,6-trinitrotoluene, has become highly prevalent in soil in the last century, particularly at manufacturing waste sites, mines and military conflict zones.

TNT is a toxic and persistent environmental pollutant and, in plants, it accumulates in the roots, inhibiting growth and development.

"Explosives such as TNT are toxic not only to plants but also animals, microbes and aquatic life," said biotechnology professor Neil Bruce of Britain's University of York, who led the study.

He said: "Large areas of land are now contaminated by explosives, and there is a pressing need to find low-cost sustainable solutions to containing these pollutants and ideally removing these pollutants from contaminated areas. Plants have the potential to do this if we can alleviate the toxicity issue."

Using a class of plant called Arabidopsis thaliana, the researchers found that a key plant enzyme - MDHAR6 - reacts with TNT, generating reactive superoxide, which is highly damaging to cells. However, a mutation in a gene that controls MDHAR6 allows these plants to have long roots and bushy leaves when grown in TNT-treated soil.

An analysis by the researchers revealed that there was no decrease in TNT concentration in the roots in the presence of the mutation. However, measuring electron activity revealed a one-electron reduction of TNT, an alteration that rendered it less toxic to the plant.

By targeting this enzyme in relevant plant species, it may be possible to produce TNT-resistant plants to revegetate and remediate explosives at contaminated sites such as military live-fire training ranges and manufacturing waste sites, the researchers said.

"Only by eliminating the acute phytotoxicity of TNT can plant-based systems be successfully used to clean up contaminated sites," said study author Liz Rylott. "Our work is an important step on that journey."

The findings were published in US journal Science on Thursday.

TNT has been used as an explosive for more than a century. Vast quantities have been used, polluting sites such as mines and war zones.

XINHUA, REUTERS

A version of this article appeared in the print edition of The Straits Times on September 05, 2015, with the headline 'Mutated plants may help clean soil'. Print Edition | Subscribe