Production of low‐Cs⁺ rice plants by inactivation of the K⁺ transporter OsHAK1 with the CRISPR‐Cas system

Abstract

The occurrence of radiocesium in food has raised sharp health concerns after nuclear accidents. Despite being present at low concentrations in contaminated soils (below μm), cesium (Cs ) can be taken up by crops and transported to their edible parts. This plant capacity to take up Cs from low concentrations has notably affected the production of rice (Oryza sativa L.) in Japan after the nuclear accident at Fukushima in 2011. Several strategies have been put into practice to reduce Cs content in this crop species such as contaminated soil removal or adaptation of agricultural practices, including dedicated fertilizer management, with limited impact or pernicious side-effects. Conversely, the development of biotechnological approaches aimed at reducing Cs accumulation in rice remain challenging. Here, we show that inactivation of the Cs -permeable K transporter OsHAK1 with the CRISPR-Cas system dramatically reduced Cs uptake by rice plants. Cs uptake in rice roots and in transformed yeast cells that expressed OsHAK1 displayed very similar kinetics parameters. In rice, Cs uptake is dependent on two functional properties of OsHAK1: (i) a poor capacity of this system to discriminate between Cs and K ; and (ii) a high capacity to transport Cs from very low external concentrations that is likely to involve an active transport mechanism. In an experiment with a Fukushima soil highly contaminated with Cs , plants lacking OsHAK1 function displayed strikingly reduced levels of Cs in roots and shoots. These results open stimulating perspectives to smartly produce safe food in regions contaminated by nuclear accidents.

Variations in radioactive cesium accumulation in wheat germplasm from fields affected by the 2011 Fukushima nuclear power plant accident

“…Thus, RCs absorption and translocation appear to be controlled by different mechanisms in wheat, and RCs accumulation in the grain should be analyzed by carefully discriminating between absorption and translocation. The various mechanisms of RCs uptake in relation to K transporters have been reviewed 1,8 , and recently, several possible transporters involved in regulating RCs uptake have been reported 23,24,47 . Kojima et al also detected large variations among rice varieties in RCs translocation from shoot to grain 20 .…”

Recent Advances in Radioisotope Imaging Technology for Plant Science Research in Japan

“…Therefore, the movements of pollutants normalized by those of essential elements can provide important information for comparing or understanding the behavior of pollutants under specific conditions. Recent studies indicated both similarity and specificity in the behavior of potassium and cesium in plants [44,45]. The difference in their behavior suggests the unique nature of plant transporters towards elemental affinity, even if the elements have a high chemical similarity.…”

Hunger and sustainability

“…also collaborate). Using the C.R.I.S.P.R./Cas9 system, they have developed a variety of rice that is capable of not selectively absorbing the caesium from the earth and that this radioactive substance does not contaminate the edible parts of the plant (Nieves-Cordones, 2017;Nieves-Cordones et al, 2017).…”