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 + 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.

Pharmacological and gene regulation properties point to the SlHAK5 K+ transporter as a system for high‐affinity Cs+ uptake in tomato plants

“…Potassium starvation has been shown to induce a high‐affinity Cs + uptake in Arabidopsis plants (Genies et al ). We studied the effect of K + starvation on Cs + accumulation when Cs + was present at micromolar concentrations in tomato plants.…”

“…In Arabidopsis, in addition to AtHAK5, non‐selective cation channels have been also suggested to contribute to Cs + uptake from micromolar concentrations (Kanter et al , Genies et al ). However, in rice, this may not be the case because OsHAK1 knocked‐out lines do not show neither high‐affinity Cs + nor K + uptake (Chen et al , Nieves‐Cordones et al ).…”

“…The question is how plants, especially crops, accumulate Cs + when present at micromolar concentrations. The high‐affinity K + transporter AtHAK5 has been suggested as a pathway for NH 4 + ‐sensitive high‐affinity Cs + uptake (Hampton et al , Qi et al , Genies et al ). Very recently, a couple of studies on the molecular mechanisms of radiocesium uptake from micromolar concentrations have been reported for rice (Ishikawa et al , Nieves‐Cordones et al ).…”

“…In agreement with this, inhibition of K + uptake by Cs + has been described (Epstein and Hagen , Sheahan et al , Maathuis and Sanders , White and Broadley , Adams et al ). Reverse genetics and pharmacological analyses have allowed the identification of several routes for Cs + uptake in Arabidopsis, Riccia fluitans and rice (Heredia et al , Caballero et al , Genies et al , Nieves‐Cordones et al ). These studies point to non‐selective cation channels (NSCCs) and HAK5‐like transporters as candidates for low‐ and high‐affinity Cs + uptake, respectively.…”

Disruption ofAtHAK/KT/KUP9enhances plant cesium accumulation under low potassium supply

“…Accumulation experiments in plants were performed in hydroponics conditions with the nutritive solution described above. Protocol for long-term Cs + accumulation assays in hydroponics conditions is described elsewhere (Genies et al, 2017). Briefly, after acclimation to hydroponics, 25 days-old (± 1 day) plants were grown in 10 or 3000 µM K + -solution during 5 days and then exposed for 7 days to 1 µM Cs + .…”