Rice Na absorption mediated by OsHKT2;1 affected Cs translocation from root to shoot under low K environments.

Cs diffused into the environment due to a nuclear power plant accident has caused serious problems for safe crop production. In plants, Cs is similar in its ionic form to K. Cs is absorbed and transported mainly by the K transport mechanism. However, the full picture of the genes contributing to Cs transport and the transport mechanism of rice is still unclear. This study focused on OsHKT2;1, a candidate Cs transporter under low K conditions. To verify the ability of OsHKT2;1 to transport Cs, the mutant () was grown in a Cs-contaminated paddy field in Fukushima. The Cs concentration in aboveground was higher than in the wild type (WT), and the K concentration in these samples did not change between WT and , whereas the Na concentration was lower in . Uptake experiments with radioactive tracers (Na, K, and Cs) in hydroponic systems with different elemental compositions showed a negative correlation between Na and Cs accumulation in rice shoot cultivated under low K conditions. These results indicated that OsHKT2;1 does not directly contribute to Cs uptake but is an important factor in regulating Cs translocation by controlling Na accumulation. This indicates the possibility of controlling rice Cs content by regulating the Na environment during cultivation.