Functions as a v-SNARE responsible for targeting AtELP-containing vesicles from the trans-Golgi network (TGN) to the prevacuolar compartment (PVC) and mediates liposome fusion (PubMed:10397763, PubMed:24021022). May be also involved in retrograde traffic to the cis-Golgi (By similarity). Promotes the formation of vacuolar membrane 'bulbs' (PubMed:21645145). Necessary to deliver proteins to the lytic vacuole, but seems not involved in storage proteins transport (PubMed:17360696). Required for amyloplast sedimentation in the endodermis during shoot gravitropism, which are thus acting as statoliths (PubMed:11826298, PubMed:15797025). Expression in the endodermis is essential for the shoot gravitropic response, whereas expression in other tissues may be responsible for the correct stem and leaf shape (PubMed:9210330, PubMed:11826297, PubMed:15797025). Forms SNARE complexes with the t-SNAREs SYP51 and either SYP21 or SYP22 in the PVC, and with a much lower affinity with SYP61 in the TGN (PubMed:15797025). Does not interact with SYP41, SYP42 or VPS45. Binds to EPSIN1. Interacts with SCYL2B (PubMed:28751315). Expressed in roots, stems, flowers and leaves. Abnormal amyloplast sedimentation and gravitropism in both inflorescence stems and hypocotyls with elongated stems in a zigzag fashion, due to narrower angles in internodes mediated by aberrant cell shapes (PubMed:9210330, PubMed:11826297, PubMed:11826298, PubMed:15797025). Reduced formation of vacuolar membrane 'bulbs' (PubMed:21645145). Altered transport of proteins to the lytic vacuole (PubMed:17360696). Small and wrinkled rosette leaves. Fragmentation and vesiculation of vacuoles mostly in cortex cells of the inflorescence stem in comparison to endodermal cells. Belongs to the VTI1 family.