Abstract
SYP2 proteins are a subfamily of Qa-SNAREs that are possibly responsible for protein trafficking between prevacuolar compartments (PVC) and vacuoles. Arabidopsis thaliana SYP22/VAM3/SGR3 and SYP21/PEP12 proteins function independently, and are yet both reported to be essential for male gametophytic viability. Here, we systematically examined the redundancy of three SYP2 paralogues (i.e., SYP21, 22, and 23). Surprisingly, no visible phenotypes were observed, even in the double knockout syp21/pep12 syp23/plp. A deficiency of either SYP21/PEP12 or SYP23/PLP in a syp22 background resulted in a defect in vacuolar protein sorting. A GFP-SYP23/PLP fusion localized to the cytosol. The immunoprecipitation analysis showed that SYP23/PLP interacted with vacuolar Qb- and Qc-SNAREs, VTI11 and SYP5, respectively, suggesting that SYP23/PLP is able to form a SNARE complex anchoring the membrane. Thus, SYP2 proteins, including cytosolic SYP23/PLP, appear to function redundantly in vacuolar trafficking and plant development.
(1) Shirakawa, M. et al, Plant Cell Physiol., 50, 1319-1328 (2009).
(2) Shirakawa, M. et al, The Plant Journal., in press.
