TNT hurts. Trinitrotoluene, the chemical that makes dynamite so physically volatile, also has the property of causing ecological and physiological devastation on a cellular level: Exposure to the chemical in drinking water can put humans at a higher risk of liver damage and cancer (0.1 mg/L of TNT in water translates to an estimated 1 in 10,000 cancer risk). For decades, environmental scientists have been poking about for clever ways to get TNT out of contaminated soil — a tobacco plant genetically modified to enzymatically degrade TNT, for instance, made headlines in 2001. But a new hope comes in the form of a natural mutant, an Arabidopsis plant — a lanky, grassy cousin to mustard — that survives thanks to an immunity to TNT.
This discovery, published this week in Science, far from dumb luck, was the end product of growing generations of Arabidopsis in contaminated soil. The key, as science journalist William Herkewitz writes at Popular Mechanics, was finding a mutant plant that lacks a gene called MDHAR6; in normal plants, TNT relies on the MDHAR6 gene to enter the mitochondria and kill the plant. Without MDHAR6, there’s no deadly mitochondrial wrinkle. Herkewitz explains:
Within the mutant organism, “TNT is transformed by enzymes and becomes locked up, out of harm’s way, in the plant’s cell walls,” says Neil Bruce, a biologist with the team who studies how plants degrade and transform explosives. “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 genetic quirk can be exploited in plants already growing in places near TNT contamination, the scientists say. Though the mutation isn’t quite up to a super-healing factor — too much absorbed TNT can still be lethal — this is a mutation theoretically induced in any plant, as MDHAR6 is a shared gene across the vegetable kingdom.
This study is the latest in the long line of mutant plants tapped to help shape the environment. A new strain of GMO rice cuts back on methane production, lowering the global warming impact of rice paddies. Algae, too, has long been touted by alt energy fans as a plausible way to churn out green jet fuel or other liquid biofuels. Plants truly are the bomb.
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