AtSYP51/52 show functional specificity in the post-Golgi traffic and act as i-SNAREs on tonoplast

Plant SNAREs coded by genes of the same family are generally considered as redundant in promoting vesicle-associated membrane fusion events. Nonetheless the application of innovative experimental approaches evidenced that members of the same gene family often have different functional specificities. The role of the two closely related Qc-SNAREs, the AtSYP51 and the AtSYP52 in the vesicle sorting to the central vacuole has been investigated. SYP5 proteins appeared to have functional specificity and to be part of a new functional class, the inhibitory SNAREs (i-SNAREs). When transiently over-expressed, the SYP51 and the SYP52 distributed between the TGN and the tonoplast. Our data demonstrate that these SYPs act as t-SNARE when present on the membrane of TGN/PVC, whereas they behave as i-SNARE when they accumulate on the tonoplast. A higher level of complexity emerges for functional classification of plant SNAREs