Figure 5. AtKEAs have strict pH requirements in mediating K⁺ transport in yeast.

(A) The cDNAs of AtKEAs, AtNHX1and ScNHX1 were subcloned into the yeast expression vector pDR196 and transformed into strain AXT3 (ena1-4 nha1 nhx1). Strains were spotted onto AP plates containing 800mM KCl at pH 4.5, 5.8 or 7.5. (B) The cDNAs of AtKEAs, AtCHX17 and ScKHA1 were subcloned into the yeast expression vector pDR196 and transformed into strain AXT4K (ena1-4 nha1 nhx1 kha1). Strains were spotted onto AP plates containing 0.1mM KCl at pH 4.5, 5.8 or 7.5. Cells were normalized in water to A₆₀₀ of 0.4. Aliquots (4μL) from normalized yeast cultures or 10-fold serial dilutions were spotted onto AP plates. The strains were grown at 30°C for 3 days.