Practice question

Arabidopsis GNOM, also known as EMB30 or VAN7, encodes brefeldin A-sensitive ARF-GEF, guanine nucleotide exchange factor for ADP-ribosylation factor small GTPases. It localizes to recycling endosomes and trans-Golgi network regulating vesicle budding required for polar cargo delivery. Principal cargo includes PIN1 and related PIN auxin efflux carriers whose polar plasma membrane localization depends on GNOM-mediated endosomal recycling. Disruption impairs directional auxin transport causing embryonic and post-embryonic defects resembling auxin transport inhibitor treatments, revealing link between membrane trafficking machinery and hormonal patterning controlling embryogenesis and lateral root development.