title: Functional redundancy between trans-Golgi network SNARE family members in Arabidopsis thaliana.
abstract: BACKGROUND
  Vesicle fusion is an essential process for maintaining the structure and function of the endomembrane system. Fusion is mediated by t-SNARE (soluble N-ethylmaleimide-sensitive factor attachment protein receptor) fusion proteins on the target membrane and v-SNAREs on the vesicle membrane; v-and t-SNAREs interact with each other, driving vesicle fusion with the target membrane. The Arabidopsis thaliana trans-Golgi network resident SNAREs SYP41 and VTI12, along with YKT61/62, have been shown to function in vesicle fusion in vitro, consistent with immunoprecipitation results showing their interaction in Arabidopsis cell extracts. Conflicting published results have indicated that SYP4 family members are either functionally redundant or have distinct and essential functions; the reason for this discrepancy is unclear.
  
  
  RESULTS
  Here we used a proteoliposome fusion assay to demonstrate that SYP42 and SYP43 can substitute for SYP41 in driving lipid mixing, providing support for functional overlap between family members. Previous reports have also suggested that VTI11 and VTI12 SNAREs show partial overlap in function, despite having mostly distinct localizations and binding partners. We show that VTI11 can substitute for VTI12 in in vitro lipid mixing reactions, providing molecular support for the genetic evidence for partial functional redundancy in vivo.
  
  
  CONCLUSIONS
  Our data provide biochemical evidence for functional overlap in membrane fusion between members of the SYP4 or VTI1 SNARE groups, supporting previous genetic data suggesting redundancy.
authors.affiliation: Department of Genetics, Development and Cell Biology, Iowa State University, Ames, IA 50011, USA. bassham@iastate.edu.
authors.forename: Sang-Jin
authors.initials: SJ
authors.lastname: Kim
authors.forename: Diane C
authors.initials: DC
authors.lastname: Bassham
mesh_terms: D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D008081:Liposomes / Q000737:chemistry / Q000378:metabolism; D008561:Membrane Fusion; D050765:Qa-SNARE Proteins / Q000235:genetics / Q000378:metabolism; D050766:Qb-SNARE Proteins / Q000235:genetics / Q000378:metabolism; D011994:Recombinant Proteins / Q000096:biosynthesis / Q000235:genetics; D050600:SNARE Proteins / Q000235:genetics / Q000378:metabolism*; D021601:trans-Golgi Network / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; D008081:Liposomes; D050765:Qa-SNARE Proteins; D050766:Qb-SNARE Proteins; D011994:Recombinant Proteins; D050600:SNARE Proteins; C541273:SYP41 protein, Arabidopsis; C120751:vesicle transport v-SNARE 11 protein, Arabidopsis; C120752:vesicle transport v-SNARE 12 protein, Arabidopsis
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