Vesicle trafficking protein that functions in the secretory pathway (By similarity). Together with SYP61, regulates the post-Golgi trafficking of the aquaporin PIP2-7 to the plasma membrane, thus modulating cell membrane water permeability (PubMed:25082856). Part of the t-SNARE complex (PubMed:11718726, PubMed:21826108). Binds to SNAP33 (PubMed:11718726). Colocalizes with SYP61 and PIP2-7 in trafficking vesicles and at the plasma membrane (PubMed:25082856). Interacts with SYP61 and PIP2-7 (PubMed:25082856). Expressed at low levels in roots, stems, flowers and leaves. Ninefold induction within 30-min exposure to abscisic acid and after 48 hours drought stress. Abnormal PIP proteins (e.g. PIP1-4, PIP2-1 and PIP2-7) trafficking and subcellular localization leading to a reduced levels at the plasma membrane. Belongs to the syntaxin family.