부산대학교 도서관

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, Ca and La, 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.