Cesium Inhibits Plant Growth Primarily Through Reduction of Potassium Influx and Accumulation in Arabidopsis
2019
Adams, Eri | Miyazaki, Takae | Saito, Shunya | Uozumi, Nobuyuki | Shin, Ryoung
Cesium (Cs⁺) is known to compete with the macronutrient potassium (K⁺) inside and outside of plants and to inhibit plant growth at high concentrations. However, the detailed molecular mechanisms of how Cs⁺ exerts its deleterious effects on K⁺ accumulation in plants are not fully elucidated. Here, we show that mutation in a member of the major K⁺ channel AKT1–KC1 complex renders Arabidopsis thaliana hypersensitive to Cs⁺. Higher severity of the phenotype and K⁺ loss were observed for these mutants in response to Cs⁺ than to K⁺ deficiency. Electrophysiological analysis demonstrated that Cs⁺, but not sodium, rubidium or ammonium, specifically inhibited K⁺ influx through the AKT1–KC1 complex. In contrast, Cs⁺ did not inhibit K⁺ efflux through the homomeric AKT1 channel that occurs in the absence of KC1, leading to a vast loss of K⁺. Our observation suggests that reduced K⁺ accumulation due to blockage/competition in AKT1 and other K⁺ transporters/channels by Cs⁺ plays a major role in plant growth retardation. This report describes the mechanical role of Cs⁺ in K⁺ accumulation, and in turn in plant performance, providing actual evidence at the plant level for what has long been believed, i.e. K⁺ channels are, therefore AKT1 is, ‘blocked’ by Cs⁺.
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