Plays an important role in maintaining plasma membrane integrity during freezing and osmotic stresses. May function in membrane resealing during calcium-dependent freezing tolerance. May regulate endocytosis and endosome recycling at the plasma membrane and cell-to-cell trafficking of cabbage leaf curl virus (CaLCuV) and tobacco mosaic virus (TMV) movement proteins via plasmodesmata. Interacts with cabbage leaf curl virus (CaLCuV) BC1 protein and tobacco mosaic virus (TMV) MP protein (PubMed:20133785). Interacts with ROSY1 (PubMed:27044028). A number of isoforms are produced. According to EST sequences. Expressed in roots, shoots, rosette and cauline leaves, inflorescences, and siliques. In roots, expressed in vascular bundle, epidermis, the differential zone of the tips of root hairs, and the quiescent center and columella of root tips. Reduced growth. Phospholipid binding to the first C2 domain is calcium-dependent, but binding to the second C2 domain is calcium-independent. Belongs to the synaptotagmin family.