The SNARE complex is a key regulator of vesicular traffic, executing membrane fusion between transport vesicles or organelles and target membranes. A functional SNARE complex consists of four helical bundles, three of which are supplied by Q-SNAREs and another from an R-SNARE. Arabidopsis thaliana VAMP727 is an R-SNARE, with homologs only in seed plants. We have found that VAMP727 colocalizes with SYP22/ VAM3, a Qa-SNARE, on a subpopulation of prevacuolar compartments/endosomes closely associated with the vacuolar membrane. Genetic and biochemical analysis including co-immunoprecipitation from Arabidopsis lysate indicates that VAMP727 forms a complex with SYP22, VTI11, and SYP51 and that this complex plays a crucial role in vacuolar transport, seed maturation, and vacuole biogenesis. We suggest that the VAMP727 complex mediates the membrane fusion between the prevacuolar compartment and the vacuole that has evolved as an essential step for seed development.

Program member
Akihiko Nakano (Department of Biological Sciences, Graduate School of Science)

Figure 1. VAMP727 complex is essential for normal development of seeds.
Yellowish vamp727syp22 double mutant seeds could not germinate after dehydration while they were viable when cultured before dehydration.

Figure 2. VAMP727 complex is required for vacuolar transport and vacuole morphogenesis.
An artificial cargo for the vacuole (GFP-CT24) was missecreted in vamp727syp22 double mutant. Fragmentation of vacuoles was also observed in the double mutant.