Figure 3.

Expression of AtHKT1 and HKT1 constructs in S. cerevisiae CY162. (a) Complementation of K⁺-uptake deficiency by the various HKT1 and AtHKT1 constructs. CY162 cells expressing AtHKT1 and HKT1 constructs were plated on 1 mM K⁺ in a dilution series from OD₆₀₀ = 1 to OD₆₀₀ = 10⁻⁴. Only constructs with a glycine at the predicted filter position in P-loop A (68 in AtHKT1, 91 in HKT1) suppressed the trk1,2 phenotype. The media were supplemented with 1 mM Na⁺. (b) Dependence of K⁺-uptake complementation on external Na⁺. The same experiment as shown in a was performed in the absence of Na⁺. (c) Expression of AtHKT1 and HKT1 constructs in the Na⁺ hypersensitive yeast strain G19. Cells were plated on 50 mM Na⁺, 1 mM K⁺ in a dilution series from OD₆₀₀ = 1 to OD₆₀₀ = 10⁻⁴.