The U.S. Department of Defense estimates that around 10 million hectares worldwide have been contaminated.Researchers have discovered what makes TNT so toxic to plants and one simple mutation that allows it to be absorbed safely.
Biologists from the University of York in the United Kingdom made the discovery and published the results in the journal Science. It is common knowledge that the pollution from the popular explosive wrecks havoc on the environment, but this group set out to study exactly how the TNT reacts with plant cells.
“Large areas of land are now contaminated by explosives and there is a pressing need to find low-cost sustainable solutions to containing these areas,” said Neil Bruce, one of the biologists studying the TNT plants. “Plants have the potential to do this if we alleviate the toxicity issue.”
Working with a small flowering plant known as Arabidopsis thaliana, researchers discovered that a gene called MDHAR6 was the culprit in the death of plants exposed to TNT. The MDHAR6 serves as a self-defense mechanism that protects the plant from toxic molecules known as reactive oxygen species (ROS).
The problem is that when TNT molecules make their way into plant cells, they use the enzymes the MDHAR6 gene produces – enzymes that are supposed to make vitamin C — to create the toxic ROS chemicals, while draining the plant’s mitochondrial fuel supply at the same time.
The surprising twist was that the biologists discovered that the plants flourishing in a TNT-polluted area did not have this MDHAR6 gene. Instead, these plants absorbed the TNT, broke it down and stored it in their hardy cell walls.
“TNT is transformed by enzymes and becomes locked up, out of harm’s way, in the plant’s cell walls,” Bruce said. “If an animal were to consume that plant, that transformed TNT would simply pass right through it. That’s because it’s tightly bound up in non-digestible material. It wouldn’t be toxic to the animal.”
The good news is that aside from being TNT-resistant, the mutated plants are indistinguishable from plants with the gene. This means that it comes down to straightforward plant breeding, and scientists can use almost any plant for the toxic cleanup once the MDHAR6 gene is removed.
Wild grasses that already grow on test firing ranges would be an ideal subject.
Still, the mutant plants aren’t invincible. Scientists say enough TNT could kill them.
“But you’d need quite a lot,” Bruce said. “What’s important is that we found the plants could survive concentrations of TNT at the upper end of what you’d expect to find at a contaminated site.”
