Boron is considered to be taken up by plants in the form of boric acid and transported to aerial portions. A boron transporter, BOR1, was isolated with the use of
Arabidopsis thaliana mutant
bor1-1. Expression of BOR1 in yeast cells reduced B concentration in the cell, suggesting that BOR1 is an efflux type transporter of B. BOR1 is expressed in pericycle in the root of the wild type plants and
bor1-1 mutant plants do not exhibit active B transport to aerial portions of plants. Our physiological analysis suggested that in the roots of Arabidopsis, B is passively transported from soil solution to stele and transported actively in to xylem to be translocated to aerial portions of plants. BOR1 is a B-efflux transporter responsible for the active loading of B to xylem. BOR1 is the first B transporter identified in the living systems and will be a key molecule for the understanding of molecular mechanisms of B transport.
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