Mutation for bioremediation

Margarita Paimakova, Vesti 

Trinitrotoluene, or TNT (TNT) is an explosive chemical often used for industrial and military purposes. Its detonation is not just an explosion, but a number of dangerous consequences: 2% of the incombustible substances contained in it can cause serious health problems in humans and animals, as well as poison the soil.

In order for grass to start growing again at the explosion site, it is required to clean it with excavators. Recently, scientists have figured out how to grow some genetically modified weeds that can pull TNT pollution from the soil. (It seems that the translator got it wrong: an article in Science says that researchers using genome sequencing found plants with natural mutations in this gene – VM.) This approach, when applied in practice, will be much cheaper than the traditional one.

TNT pollutes vast territories in the world, but people, as a rule, do not even know about it: the military in various countries are testing TNT-based explosives at their landfills, and in most regions toxins in the soil have been preserved since the time of long-standing military conflicts.

The toxin leads to various diseases, including liver dysfunction and cancer. It is harmful to all kinds of animals, but at the same time it can bind with soil microbes and thus "travel" through the soil.

"We have to recommend the military to think about reducing the use of pollutants in their tests," says plant geneticist Neil Bruce from York University in the UK. – But today we are working on solving this issue, the key to which lies in plants" (see the press release of Fighting explosives pollution with plants).

For more than ten years, Bruce has been breeding plants for soil reclamation. He created a genetically modified variety of the rhesus thaliana (Arabidopsis thaliana), a weed plant that takes TNT from the soil and blocks it in its cell walls. Ordinary plants are also able to take the toxin from the soil for a while, but a very dose of poison becomes destructive. A genetically modified plant with a mutation in the MDHAR6 gene is helped by its long roots and thick leaves. 

Rezukhovidki are relatives of mustard. Scientists began their experiments by planting a lot of these plants on soil contaminated with TNT.

"We have identified one variety that has demonstrated significant resistance to toxins," explains Bruce. "We already knew the genetic sequence of the plant and were able to pinpoint the gene encoding the enzyme that enables the plant cell to generate energy."

In the left pots – ordinary arabidopsis plants, in the right – with mutations in the monodehydroascorbate reductase gene.

At the top – ordinary soil, at the bottom – contaminated with TNT explosion products.A snapshot from an article in Science – VM.

When these small cellular organelles encounter TNT, they try to transform it into something that the plant can feed on. But the lack of oxygen turns the TNT molecule into a more reactive form, as a result of which the toxin acquires a volatile state.

Bruce and his colleagues have identified a gene that causes mitochondria to simply ignore TNT, so that the plant simply stores the toxin in its cell walls. This genetic mutation periodically manifests itself in all kinds of different plants, so, in fact, they can be useful for cleaning the soil.

In their work, the researchers used traditional methods of breeding, not genetic modification, besides, the toxin-filled rhesus cells, apparently, are not even dangerous for herbivores, since they cannot digest them.

A scientific article (Johnston et al., Monodehydroascorbate reductase mediates TNT toxicity in plants) was published by the journal Science.

Portal "Eternal youth" http://vechnayamolodost.ru

07.09.2015