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. Despitebeing present at low concentrations in contaminated soils (belowlM), cesium (Cs+) can be taken up bycrops and transported to their edible parts. This plant capacity to take up Cs+from low concentrations hasnotably affected the production of rice (Oryza sativaL.) in Japan after the nuclear accident at Fukushima in2011. Several strategies have been put into practice to reduce Cs+content in this crop species such as con-taminated soil removal or adaptation of agricultural practices, including dedicated fertilizer management,with limited impact or pernicious side-effects. Conversely, the development of biotechnological approachesaimed 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 riceplants. Cs+uptake in rice roots and in transformed yeast cells that expressed OsHAK1 displayed very similarkinetics parameters. In rice, Cs+uptake is dependent on two functional properties of OsHAK1: (i) a poorcapacity of this system to discriminate between Cs+and K+; and (ii) a high capacity to transport Cs+fromvery low external concentrations that is likely to involve an active transport mechanism. In an experimentwith a Fukushima soil highly contaminated with137Cs+, plants lacking OsHAK1 function displayed strikinglyreduced levels of137Cs+in roots and shoots. These results open stimulating perspectives to smartly producesafe food in regions contaminated by nuclear accidents