Schematic presentation for B uptake system and its regulation in rice roots. B uptake in rice roots is mediated by OsLsi1 and OsBOR1, which are polarly localized at the distal and proximal side of both exodermis and endodermis. OsLsi1 is not regulated at both transcriptional and posttranslational level, while OsBOR1 protein is degraded in response to high B concentrations through clathrin-independent pathway. Thickness of arrows roughly represents the contribution of each step.