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 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 Ba(2+), Ca(2+) and La(3+), but not by 10 microM 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.
Broadley
M R
MR
Horticulture Research International, Wellesbourne, Warwick CV35 9EF, UK. martin.broadley@hri.ac.uk
Escobar-Gutiérrez
A J
AJ
Bowen
H C
HC
Willey
N J
NJ
White
P J
PJ
D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins; D002586:Cesium / Q000378:metabolism*; D017136:Ion Transport; D010940:Plant Proteins / Q000235:genetics*; D011188:Potassium / Q000378:metabolism*; D015221:Potassium Channels / Q000235:genetics*
D029681:Arabidopsis Proteins; D010940:Plant Proteins; D015221:Potassium Channels; C074500:AKT1 protein, Arabidopsis; D002586:Cesium; D011188:Potassium