Development of the root pole and cell patterning in Arabidopsis roots

The root forms at the basal end of an axis that is set up early in embryoge nesis, and recent genetic analysis has indicated that auxin transport is re quired for the formation of the root pole. Drug studies show that auxin tra nsport is also required for the maintenance of the tissue organisation in t he seedling root. These studies support existing models for tissue patterni ng that involve canalised auxin flow. Molecular insights into the mechanism of cell-type specification and patterning has come from the epidermis wher e positionally controlled cell specification is regulated by a cascade of t ranscription factors.