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Plant Physiology
Vol. 136, No. xx, 2004; Pages: 3824–3837


Cesium Toxicity in Arabidopsis1

Corrina R. Hampton, Helen C. Bowen, Martin R. Broadley, John P. Hammond, Andrew Mead, Katharine A. Payne, Jeremy Pritchard, and Philip J. White*

Warwick HRI, Warwick CV35 9EF, United Kingdom (C.R.H., H.C.B., J.P.H., A.M., K.A.P., P.J.W.);
School of Biological Sciences, The University of Birmingham, Birmingham B15 2TT, United Kingdom (C.R.H., J.P.); and Plant Sciences Division, University of Nottingham, Sutton Bonington Campus, Loughborough LE12 5RD, United Kingdom (M.R.B., J.P.H., K.A.P.).


Abstract

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]aga 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.

Keywords:Cesium,potassium,Arabidopsis thaliana,cytoplasm,aluminosilicate mineral pollucite,Arabidopsis,Cesium Toxicity,radionuclides.


Corresponding author: Fax 44–(0)24–76574500

E-mail: philip-j.white@warwick.ac.uk

 

 
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