Abstract
Boron (B) is essential in higher plants especially for cross-linking pectic polysaccharides to maintain cell wall function. Boron is often present at low concentrations in the environment and B deficiency hampers crop production in many parts of the world. It has been suggested that plant roots take up B mainly as uncharged boric acid (B(OH)3) by passive diffusion across the lipid bilayer and putative membrane proteins. However, the molecular identity of boric acid importers and their physiological significance have not yet been uncovered in planta. We conducted a transcriptome analysis and identified NIP5;1, a member of the major intrinsic protein family, as a gene up-regulated in B-deficient roots of Arabidopsis thaliana. We show that NIP5;1 is a plasma membrane boric acid channel crucial for B uptake to support plant growth under B limitation.
