Effects of Polylinker uATGs on the Function of Grass HKT1 Transporters Expressed in Yeast Cells

HvHKT1 mediates K(+) or Na(+) uniport in yeast cells if the expression promoter is joined directly to the HvHKT1 cDNA, and Na(+)-K(+) symport if a 59 nucleotide polylinker is inserted. Our results show that three ATG triplets in the polylinker decreased the synthesis of the transporter and that the lower amount of transporter caused the functional change. With the rice HKT1 cDNA, the 59 nt polylinker changed the mode of Na(+) uptake from K(+)-insensitive to K(+)-inhibitable. These two modes of Na(+) uptake also occurred in rice plants.