Coordinated polar localization of auxin efflux carrier PIN1 by GNOM ARF GEF

The plant hormone auxin is transported in a polar manner along the shoot-ro ot axis, which requires efflux carriers such as PIN1. Asymmetric localizati on-of PIN1 develops from a random distribution in Arabidopsis early embryog enesis. Coordinated polar localization of PIN1 is defective in gnom embryos . GNOM is a membrane-associated guanine-nucleotide exchange factor on ADP-r ibosylation factor G protein (ARF GEF). Thus, GNOM-dependent vesicle traffi cking may establish cell polarity, resulting in polar auxin transport.