The yin-yang of uranium in Arabidopsis

Uranium isn’t something people tend to think about in a positive light. But scientists from the Université Grenoble Alpes and the French Alternative Energies and Atomic Energies Commission (CEA) have shown how the toxic radionuclide can be beneficial in plants.

Uranium is naturally present in the environment and can be redistributed by mining, military and agricultural activities. Accumulations of uranium, chemotoxic for all living organisms, can build up to concentrations that can potentially be harmful for agricultural systems and human health.

Plants absorb uranium from the soil. Once in the plant, it is incorporated into biomass and enters the food chain. Understanding the variety of mechanisms that control the response and adaptation of plants to uranium-induced stress is a prerequisite for selecting species suitable for phytoremediation and improving food safety.

Researchers experimented with a mutant of Arabidopsis thaliana (mutant irt1), which is less able to absorb iron, an essential element for growth. They found that the plant exhibited typical symptoms of iron deficiency – yellowed leaves and a reduction in photosynthesis – unless it was treated with uranium, in which case the symptoms were alleviated.

Image: Yin-yang effects of uranium on the physiology of the wild plant Arabidopsis thaliana (WT) and mutant irt1. After 4 to 5 weeks of hydroponic culture under standard conditions, Arabidopsis WT and irt1 plants are treated with uranyl nitrate, in the presence of high phosphate (HP) concentrations or low phosphate (LP) concentrations. Observations after a 21-day exposure in the presence of 50 μM uranyl nitrate.
Yin-yang effects of uranium on the physiology of the wild plant Arabidopsis thaliana (WT) and mutant irt1. After four to five weeks of hydroponic culture under standard conditions, Arabidopsis WT and irt1 plants are treated with uranyl nitrate, in the presence of high phosphate (HP) concentrations or low phosphate (LP) concentrations. Observations after a 21-day exposure in the presence of 50 μM uranyl nitrate.

The researchers suggest that the unexpected beneficial effect of uranium on the mutant Arabidopsis plants is due to competition between iron and uranium for complexation with phosphate. When the plants are grown with sufficient phosphate, the uranium steps in and releases the iron from iron-phosphate complexes, so that it can be used by the plant, reducing the symptoms of iron deficiency. When the plants are grown without enough phosphate, uranium is absorbed more efficiently by the plant, and it becomes toxic.

Understanding the yin and yang of uranium – how it interacts with the inner machinery of plants, at a cellular level – should help researchers to understand how plants can be better adapted to ensure food safety and help to clear contaminated land in the future.

Adapted from an original press release.

Read the paper: Berthet, S., Villiers, F., Alban, C., Serre, N. B. C., Martin-Laffon, J., Figuet, S., Boisson, A.-M., Bligny, R., Kuntz, M., Finazzi, G., Ravanel, S. and Bourguignon, J. (2017) Arabidopsis thaliana plants challenged with uranium reveal new insights into iron and phosphate homeostasisNew Phytologist. doi: 10.1111/nph.14865


 

Mike Whitfield (@mgwhitfield)
Development Coordinator
New Phytologist