Roles of BOR1, DUR3, and FPS1 in boron transport and tolerance in Saccharomyces cerevisiae


  • Present address: Akira Nozawa, Cell-free Science and Technology Research Center, Ehime University, 3 Bunkyo-Cho, Matsuyama 790-8577, Japan

  • Editor: Linda Bisson

Correspondence: Toru Fujiwara, Biotechnology Research Center, The University of Tokyo, 1-1-1 Yayoi, Bunkyo-ku, Tokyo 113-8657, Japan. Tel.: +81 3 5841 2407; fax: +81 3 5841 2408; e-mail:


The roles of three membrane proteins, BOR1, DUR3, and FPS1, in boron (B) transport in yeast were examined. The boron concentration in yeast cells lacking BOR1 was elevated upon exposure to 90 mM boric acid, whereas cells lacking DUR3 or FPS1 showed lower boron concentrations. Compared with control cells, cells overexpressing BOR1 or FPS1 had a lower boron concentration, and cells overexpressing DUR3 had a higher boron concentration. These results suggest that, in addition to the efflux boron transporter BOR1, DUR3 and FPS1 play important roles in regulating the cellular boron concentration. Analysis of the yeast transformants for tolerance to a high boric acid concentration revealed an apparent negative correlation between the protoplasmic boron concentration and the degree of tolerance to a high external boron concentration. Thus, BOR1, DUR3, and FPS1 appear to be involved in tolerance to boric acid and the maintenance of the protoplasmic boron concentration.