Abstract
Boron has been known as an essential element for plants for 80 years, and recently shown to be essential to animals. B was considered to be passively taken up by plants. Through the studies on Arabidopsis mutant bor1-1, we showed that B transport to shoots is an active process and identified the transporter required for the active transport. This is the first B transporter identified in biological systems. The bor1-1 mutants requires a high concentration of B for normal growth. B concentration in the shoots of the mutant is lower than the wild type and tracer experiments indicated that the mutant is defective in active transport of B from roots to shoots. BOR1 was identified as AT2G47160 through positional cloning. BOR1 expression studies in plants and yeasts suggest that BOR1 is an efflux transporter of B required for active xylem loading of B.
