Soils contaminated with uranium can contaminate plants, representing a threat to humans and their environment. Nevertheless, researchers at the BIG have studied the plant Arabidopsis thaliana under varying cultivation conditions, showing that uranium can be either deleterious or beneficial, depending on the absorption levels of iron and phosphate.

In general, uranium affects the availability of iron in plants. An Arabidopsis thaliana mutant with affected iron absorption will become chlorotic (yellow leaves) when phosphate availability is sufficient. Adding uranium then causes greening of the leaves and proper plant growth. How can this be explained?

"In roots and leaves, uranium could displace inactive iron from iron-phosphate complexes to release active iron for biogenesis processes and metabolism", respond Stéphane Ravanel and Jacques Bourguignon, researchers at the BIG. "When phosphate is in limiting quantities in the medium, the bioavailability of uranium is increased and the radionuclide is absorbed more effectively by the plant. The toxic effects of uranium are thus clearly visible in the wild plant and the mutant (halting of growth)". The analyses show that one of the key mechanisms of uranium toxicity is linked to an interference with phosphate homeostasis, and more specifically to the induction of a deficiency in phosphorylated compounds.

Decontamination and food safety

Uranium is naturally present in the environment. It can be redistributed through mining, military and agricultural activities. This radionuclide, which is chemotoxic to all living organisms, can accumulate locally at concentrations that present potential risks for agrosystems and human health. Indeed, even if it is not essential for plants, uranium is absorbed from the soil and incorporated into plant biomass, thereby entering the food chain. Understanding the physiological, biochemical and molecular mechanisms that control the response and the adaptation of plants to uranium-induced stress is a prerequisite for selecting species adapted to soil decontamination and to food safety improvement.