Abstract
Boron (B) is essential for plants but toxic when present in excess. Arabidopsis thaliana BOR1 is a borate exporter for efficient B translocation under B limitation (Takano et al. 2002). Using P35S:BOR1-GFP plants, we have shown that BOR1 is regulated by B-dependent endocytosis and degradation (Takano et al. 2005).
Here we report localization and B-dependent regulation of BOR1-GFP expressed under control of the BOR1 promoter. BOR1-GFP was localized to steler cells in mature portion of roots and also to various cells in root tip under B limitation. In root tip, BOR1-GFP was preferentially localized on the plasma membrane of the proximal side of the epidermal cells. These results suggest that BOR1 functions for B transport into xylem in mature portion for root-to-shoot B translocation while it is for radial B transport towards inner portions in root tip.
