Uptake and translocation of cesium by Arabidopsis thaliana in hydroponics conditions: Links between kinetics and molecular mechanisms

Abstract Early studies have shown that cesium (Cs + ) competes with the macronutrient potassium (K + ) for uptake by plants. The present study investigates the effect of K + supply on Cs + uptake and translocation in Arabidopsis thaliana . Taking advantage of the frequent use of this model plant in previous molecular studies, we discuss the link between functional features described for transporters involved in K + (and sometimes in Cs + ) uptake and results obtained here in both Cs + influx and accumulation experiments under different K + -treatments. In low K + condition (10 μM), we observed that roots affinity for Cs + increased significantly and Cs + concentration in the external medium clearly affected the efficiency of Cs + uptake. Our results are consistent with previous molecular studies indicating the role of the high-affinity K + carrier AtHAK5 in Cs + uptake under K + -deprivation. Further experiments show that the lack of AtHAK5 has no more effect on Cs + uptake for external Cs + concentration above 100 μM. We propose that non-selective cation channels, likely involved in Cs + uptake under K + -sufficient conditions according to previous studies, could also mediate Cs + uptake under K + -starvation and high Cs + concentrations. Finally, evidences for Cs + translocation mediated by K + channels are discussed.