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

Abstract

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.

Flowering plant phylogeny and soil to plant transfer of radionuclides

“…For example, it has been suggested that l37 Cs uptake into plants is primarily through Voltage Independent Cation channels in root membranes [6]. Our research has supported this suggestion by demonstrating the irrelevance of other potential transporter proteins to 137 Cs uptake [7]. The results reported here suggest that high l37 Cs uptake in the CaryophyHales might arise from VIC channel characteristics.…”

Radioactive cesium distribution in bamboo [Phyllostachys reticulata(Rupr) K. Koch] shoots after the TEPCO Fukushima Daiichi Nuclear Power Plant disaster

“…Barkley (Mori et al 2012). The molecular mechanism of Cs absorption into cells in the top tissues may be similar to the root absorption mechanism, which occurs through K transporters (White and Broadley 2000;Broadley et al 2001;Britto and Kronzucker 2008;Kanter et al 2010;Kobayashi et al 2010). After the disaster, during the rainy season in Japan, some of the soluble components of the fallout may have moved downward on the surface of bamboo shoots into the litter on the soil surface (Nuclear Regulation Authority n.d.b) or into the surface soils below the litter layer, or could have been absorbed by the condensed aerial roots around the nodes (Fig.…”

Amelioration of soils contaminated with radionuclides: Exploiting biodiversity to minimise or maximise soil to plant transfer

“…There is also current research into Cs uptake mechanisms in plants, often with a view to genetically manipulating Cs uptake. When the genes associated with uptake mechanisms for Cs have been identified (11), or when utilising Quantitative Trail Loci that have already been described in Arabidopsis (12), the biodiversity 'landscape' described through phylogeny could provide a useful conduit to application in the field. This might be for safe crops or for those with enhanced uptake of radioceasium.…”