Intracellular vesicle trafficking and protein transport. Plays an important role in the regulation of pollen tube tip growth. Interacts with PI4KB1. Associated with membrane compartments that localize to the tips of growing pollen tubes. Specifically expressed in pollen and localized to the tips of growing pollen tubes. Defects in pollen tube growth and altered deposition of cell wall components. Belongs to the small GTPase superfamily. Rab family.