Figure 4.

Boric acid export activity of Brassica napus BOR1s in ∆atr1 and ∆bor1 yeast cells.

Boric acid toxicity growth assays under high‐B conditions in the ∆bor1 (a) and ∆atr1 (b) mutant yeast strains expressing the indicated BOR1 isoforms. Cultures of mutant yeast cells transformed with the empty vector pYeDP60u or pYeDP60u carrying AtBOR1 or the indicated BnaBOR1 cDNAs were diluted in sterile water and spotted on medium containing the indicated concentrations of boric acid. Growth behavior and survival rates of the different transformants were recorded after 5–10 days at 30°C and are shown for yeasts spotted at an OD ₆₀₀ of 0.01. All yeast growth assays were performed at least twice with independent transformation events and with consistent results. Displayed images in (a) and (b) represent groups of sub‐images assembled from different growth plates and conditions.