Influx and accumulation of Cs+ by the akt1 mutant of Arabidopsis thaliana (L.) Heynh. lacking a dominant K+ transport system

An extensive literature reports that Cs+, an environmental contaminant, enters plant cells through K+ transport systems. Several recently identified plant K+ transport systems are permeable to Cs+. Permeation models indicate that most Cs+ uptake into plant roots under typical soil ionic conditions w...

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Bibliographic Details
Published in:	Journal of experimental botany 2001-04, Vol.52 (357), p.839-844
Main Authors:	Broadley, Martin R., Escobar‐Gutiérrez, Abraham J., Bowen, Helen C., Willey, Neil J., White, Philip J.
Format:	Article
Language:	eng
Subjects:	[Cs+]ext [K+]ext Arabidopsis - genetics Arabidopsis - metabolism Arabidopsis Proteins Biological and medical sciences bromocyclicadenosinemonophosphate Br‐cAMP Caesium (Cs) cation channel Cell membranes Cell physiology Cesium - metabolism external Cs+concentration external K+concentration Fundamental and applied biological sciences. Psychology inward‐rectifying K Ion Transport KIR KOR Life Sciences Murashige and Skoog outward‐rectifying K Pharmacology Physiology phytoremediation Plant physiology Plant physiology and development Plant Proteins - genetics Plant roots Plants Plants and the Environment Plasma membrane and permeation Potassium Potassium - metabolism Potassium Channels - genetics potassium transport Salts Seedlings Sodium VIC voltage‐insensitive cation
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Summary:	An extensive literature reports that Cs+, an environmental contaminant, enters plant cells through K+ transport systems. Several recently identified plant K+ transport systems are permeable to Cs+. Permeation models indicate that most Cs+ uptake into plant roots under typical soil ionic conditions will be mediated by voltage‐insensitive cation (VIC) channels in the plasma membrane and not by the inward rectifying K+ (KIR) channels implicated in plant K nutrition. Cation fluxes through KIR channels are blocked by Cs+. This paper tests directly the hypothesis that the dominant KIR channel in plant roots (AKT1) does not contribute significantly to Cs+ uptake by comparing Cs+ uptake into wild‐type and the akt1 knockout mutant of Arabidopsis thaliana (L.) Heynh. Wild‐type and akt1 plants were grown to comparable size and K+ content on agar containing 10 mM K+. Both Cs+ influx to roots of intact plants and Cs+ accumulation in roots and shoots were identical in wild‐type and akt1 plants. These data indicate that AKT1 is unlikely to contribute significantly to Cs+ uptake by wild‐type Arabidopsis from ‘single‐salt’ solutions. The influx of Cs+ to roots of intact wild‐type and akt1 plants was inhibited by 1 mM Ba2+, Ca2+ and La3+, but not by 10 μM Br‐cAMP. This pharmacology resembles that of VIC channels and is consistent with the hypothesis that VIC channels mediate most Cs+ influx under ‘single‐salt’ conditions.
ISSN:	0022-0957 1460-2431