Figure 2.

Yeast mutant KTA40-2 expressing CHX20 is tolerant to low K⁺ at alkaline pH. A, Sensitivity to moderate NaCl stress and high KCl. CHX20 (+) or vector only (−) was expressed in a KTA40-2 mutant. Growth was tested on standard SC medium (containing 8 mm K⁺, 1.7 mm Na⁺) or medium supplemented with 100 mm NaCl or 500 mm KCl at pH 4.5 to 7.5. Cells were normalized to 1.0 A₆₀₀ and then serially diluted by 10-fold. Five microliters of each dilution was spotted. B, Tolerance to low K⁺ at pH 7.5. Yeast mutant KTA40-2 was transformed with either vector pYES-c1 alone or with pDYES-CHX20, and the culture was serially diluted and plated on SDAP-Ura at pH 4.5 to 7.5 with no added K⁺ as described above. C, K⁺ concentration dependence. KTA40-2 was serially diluted and plated on medium at pH 7.5 supplemented with 0, 1, 3, 25, and 50 mm KCl.