Abstract
SYP51 and 52 are the two members of the SYP5 Qc-SNARE gene family in Arabidopsis thaliana. These two proteins, besides their high level of sequence identity (85%), have shown to have differential functional specificity and possess a different interactome. Here we describe a unique and specific interaction of SYP51 with an ER aquaporin, AtNIP1;1 (also known as NLM1) indicated to be able to transport arsenite [As(III)] and previously localized on PM. In the present work we investigate in detail such localization in vivo and characterize the interaction with SYP51. We suggest that this interaction may reveal a new mechanism regulating tonoplast invagination and recycling. We propose this interaction to be part of a regulatory mechanism associated with direct membrane transport from ER to tonoplast and Golgi mediated vesicle trafficking. We also demonstrate that NIP1;1 is important for plant tolerance to arsenite but does not alter its uptake or translocation. To explain such phenomenon the hypothesis that SYP51/NIP1;1 interaction modifies ER and vacuole ability to accumulate arsenite is discussed.
Highlights
Membrane traffic regulation is essential to compartmentalization and proper functioning of the cell
It was shown that both SYP21 and 22 interact with VTI11 and SYP51 at the prevacuolar compartment and/or at the tonoplast, and the VTI12, SYP41/SYP42, and SYP61 sensitive factor attachment protein receptor (SNARE) form a complex at the TGN
Interactions Network analysis was performed starting from Arabidopsis SNAREs and searching only interacting candidates among transmembrane proteins belonging to the secretory system
Summary
Membrane traffic regulation is essential to compartmentalization and proper functioning of the cell. Soluble N-ethylmaleimide-sensitive factor attachment protein receptor (SNARE) proteins are the main determinants of membrane fusion specificity and are known to act forming coiled-coil interactions between specific sets of partners (Jahn and Scheller, 2006). Each organelle in the endomembrane system contains a specific group of SNAREs so that specific SNARE-complex formation is thought to provide the specificity of membrane fusion (Jahn and Scheller, 2006). The presence of a glutamine (Q) or arginine (R) residue in the SNARE domain allows to structurally classify these proteins into Q and R groups and Q-SNAREs can be further classified into Qa, Qb, and Qc (Fasshauer et al, 1998). It was shown that both SYP21 and 22 interact with VTI11 and SYP51 at the prevacuolar compartment and/or at the tonoplast, and the VTI12, SYP41/SYP42, and SYP61 SNAREs form a complex at the TGN
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