Researchers have identified a mutation in plants that allows them to break down TNT, an explosive that has become highly prevalent in soil in the last century, particularly at manufacturing waste sites, mines, and military conflict zones.

TNT, or 2,4,6-trinitrotoluene, is a toxic and persistent environmental pollutant that accumulates in the roots of plants, inhibiting growth and development. The identification of a plant mechanism that not only evades the negative impacts of TNT, but breaks down this harmful substance could lead to improved revegetation and remediation of TNT-contaminated sites.

By screening various plant lines of Arabidopsis thaliana for greater root growth in the presence of TNT, Emily Johnston and colleagues identified a mutation of the MDHAR6 gene, which allows these plants to have enhanced shoot and root biomass when grown in TNT-treated soil. The MDHAR6-mutant plants did not show tolerance to other harmful substances, indicating that the mutation is TNT-specific, and not related to a general boost in plant defenses.

Credit: Eddy Doust

An analysis by the team revealed that there was no decrease in TNT concentration in the presence of the mutation; however, measuring electron activity revealed a one-electron reduction of TNT, an alteration that rendered the explosive less toxic to the plant. The authors note that this MDHAR6 reaction with TNT could also be leveraged to produce some types of environmentally acceptable herbicides.

A Perspective by Graham Noctor explores additional surprising findings uncovered in this paper that raise new questions around the physiological role of MDHAR6 in plastids and mitochondria.

Citation: "Monodehydroascorbate reductase mediates TNT toxicity in plants," by E.J. Johnston; E.L. Rylott; E. Beynon; A. Lorenz; V. Chechik; N.C. Bruce at University of York in York, UK.