AtSYP51/52 functions diverge in the post-Golgi traffic and differently affect vacuolar sorting.

Plant SNAREs encoded by genes of the same subfamily are generally considered as redundant in promoting vesicle-associated membrane fusion events. Nonetheless the application of innovative experimental approaches highlighted that members of the same gene subfamily often have different functional specificities. In this work two closely related Qc-SNAREs, the AtSYP51 and the AtSYP52 are compared in their ability to influence different secretory pathways. Their role in the vesicle sorting to the central vacuole has been revised and they were found to have a novel inhibitory function. 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 inhibitory or interfering SNAREs (i-SNAREs) when they accumulate on the tonoplast. Moreover, the performed functional analysis indicated that the AtSYP51 and the AtSYP52 role differ in the traffic to the vacuole. The findings are a novel contribution for the functional characterization of plant SNAREs that reveal additional non-fusogenic roles.