Cesium toxicity in Arabidopsis

• Published in: Plant physiology (Bethesda) 2004-11, Vol.136 (3), p.3824-3837
• Main Authors: Hampton, C.R, Bowen, H.C, Broadley, M.R, Hammond, J.P, Mead, A, Payne, K.A, Pritchard, J, White, P.J
• Format: Article
• Language: English
• Subjects: Arabidopsis - drug effects; Arabidopsis - growth & development; Arabidopsis - metabolism; Arabidopsis thaliana; Biological and medical sciences; Cesium; Cesium - antagonists & inhibitors; Cesium - metabolism; Cesium - toxicity; Fundamental and applied biological sciences. Psychology; gene expression regulation; Gene Expression Regulation, Plant - drug effects; Genes; Genes. Genome; Industrial plants; Intoxication; Molecular and cellular biology; Molecular genetics; nutrient uptake; Physiological diseases. Varia; Phytopathology. Animal pests. Plant and forest protection; Plant growth; Plant Nutrition; Plant roots; Plant Shoots - drug effects; Plant Shoots - growth & development; Plant Shoots - metabolism; Plants; Potassium; Potassium - physiology; rhizosphere; RNA; Starvation; toxic substances; transcription (genetics)
• ISSN: 0032-0889; 1532-2548
• DOI: 10.1104/pp.104.046672

Cesium (Cs) is chemically similar to potassium (K). However, although K is an essential element, Cs is toxic to plants. Two contrasting hypotheses to explain Cs toxicity have been proposed: (1) extracellular Cs(+) prevents K(+) uptake and, thereby, induces K starvation; and (2) intracellular Cs(+) interacts with vital K(+)-binding sites in proteins, either competitively or noncompetitively, impairing their activities. We tested these hypotheses with Arabidopsis (Arabidopsis thaliana). Increasing the Cs concentration in the agar ([Cs]agar) on which Arabidopsis were grown reduced shoot growth. Increasing the K concentration in the agar ([K]agar) increased the [Cs]agar at which Cs toxicity was observed. However, although increasing [Cs]agar reduced shoot K concentration ([K]shoot), the decrease in shoot growth appeared unrelated to [K]shoot per se. Furthermore, the changes in gene expression in Cs-intoxicated plants differed from those of K-starved plants, suggesting that Cs intoxication was not perceived genetically solely as K starvation. In addition to reducing [K]shoot, increasing [Cs]agar also increased shoot Cs concentration ([Cs]shoot), but shoot growth appeared unrelated to [Cs]shoot per se. The relationship between shoot growth and [Cs]shoot/[K]shoot suggested that, at a nontoxic [Cs]shoot, growth was determined by [K]shoot but that the growth of Cs-intoxicated plants was related to the [Cs]shoot/[K]shoot quotient. This is consistent with Cs intoxication resulting from competition between K(+) and Cs(+) for K(+)-binding sites on essential proteins.