Involved in the deposition of apical pectin cap and cellulose microfibrils in pollen tubes (PubMed:23384085). Implicated in pollen tubes growth in the female transmitting tract of pistil and toward micropyles, via the perception of ovule guidance cues (PubMed:23384085). Localized at the apical plasma membrane of pollen tubes (PubMed:23384085). In the cytoplasm, observed in motile punctate vesicles (PubMed:23384085). Mostly expressed in flowers, stamen, anthers and pollen, and, to a lower extent, possibly in roots, stems, leaves and siliques. Belongs to the COBRA family. Extended N-terminus. Extended N-terminus.