FIG. 2.

The ATR1 gene provides boron resistance. (A) Wild-type strain W3031-a and its isogenic atr1Δ mutant were grown to logarithmic phase in rich (YPD) medium, and the cultures were diluted to an OD₆₀₀ of 0.2. Five microliters of each cell suspension was spotted on plates containing the indicated amounts of boric acid. The plates were incubated at 30°C for 5 days and photographed. (B) ATR1-overexpressing wild-type and atr1Δ cells were grown in the presence of the indicated concentrations of boron. Cells transformed with an empty vector were used as a control. (C) Comparisons of the boron tolerances of atr1Δ, bor1Δ, dur3Δ, and fps1Δ mutants. Overnight cultures were diluted to the indicated densities, and 5 μl of each cell suspension was spotted. The cells were grown for 3 days, and the plates were photographed.