May provide the t-SNARE function in the vacuolar assembly. Promotes the formation of vacuolar membrane 'bulbs'. Required for inflorescence stem gravitropism. Interacts with VTI11 and SYP51 to form a t-SNARE complex, but not with VPS45. Prevacuolar compartment (PVC) in roots, and junction of two vacuolar membranes in shoot apical meristem. Expressed in roots, leaves, stems, flower and green siliques. The sgr3-1 mutant has a reduced gravitropic response in inflorescence stem but a normal gravitropic response in hypocotyls. Reduced formation of vacuolar membrane 'bulbs'. Belongs to the syntaxin family.