Abstract
At3g62270 is the most similar paralog to BOR1, an efflux B transporter of Arabiodopsis. Yeast expressing At3g62270 cDNA was incubated with medium containing boron. The soluble boron concentration in cells was lower than the control, suggesting that At3g62270 is an efflux B transporter. An At3g62270 knock-out plant line showed growth inhibition in roots and shoots, and decreased boron concentration in shoots compared with wild type plants, when they were grown on medium with 0.3μM boric acid. The phenotypes were not as severe as BOR1 knock-out plants. Double knock-out plants of BOR1 and At3g62270 showed severer growth retardation than either of single knock-out plants. These knock-out plants grew normally on medium containing 30μM boric acid. We propose that At3g62270 is a boron transporter working under low boron supply condition, having a different role from BOR1 in boron transport.
