title: Functional anatomy of the Arabidopsis cytokinesis-specific syntaxin KNOLLE.
abstract: In plant cytokinesis, Golgi/trans-Golgi network-derived vesicles are targeted to the plane of cell division where they fuse with one another to form the partitioning membrane (cell plate). This membrane fusion requires a specialised syntaxin (Qa-SNARE), named KNOLLE in Arabidopsis. KNOLLE is only made during the M-phase of the cell cycle, targeted to the plane of cell division and degraded in the vacuole at the end of cytokinesis. To identify the parts of KNOLLE required for proper targeting and function in membrane fusion, we generated chimeric syntaxins comprising complementary fragments from KNOLLE and MVB-localized PEP12 (SYP21). Surprisingly, targeting of the chimeric protein was not specified by the C-terminal membrane anchor. Rather the N-terminal region including helix Ha and the adjacent linker to helix Hb appeared to played a critical role. However, deletion of this N-terminal fragment from KNOLLE (KN(Δ1-82) ) had the same effect as its presence in the chimeric protein (KN(1-82) -PEP12(64-279) ), suggesting that targeting to the plane of cell division occurs by default, i.e. when no sorting signal would target the syntaxin to a specific endomembrane compartment. Once the full-length syntaxin accumulated at the plane of division, phenotypic rescue of the knolle mutant only required the SNARE domain plus the adjacent linker connecting helix Hc to the SNARE domain from KNOLLE. Our results suggest that targeting of syntaxin to the plane of cell division occurs without active sorting, whereas syntaxin-mediated membrane fusion requires sequence-specific features.
authors.affiliation: Zentrum für Molekularbiologie der Pflanzen, Entwicklungsgenetik, University of Tübingen, Auf der Morgenstelle 3, 72076 Tübingen, Germany.
authors.forename: Sonja
authors.initials: S
authors.lastname: Touihri
authors.forename: Christian
authors.initials: C
authors.lastname: Knöll
authors.forename: York-Dieter
authors.initials: YD
authors.lastname: Stierhof
authors.forename: Isabel
authors.initials: I
authors.lastname: Müller
authors.forename: Ulrike
authors.initials: U
authors.lastname: Mayer
authors.forename: Gerd
authors.initials: G
authors.lastname: Jürgens
mesh_terms: D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D002455:Cell Division; D002462:Cell Membrane / Q000378:metabolism; D048749:Cytokinesis; D008561:Membrane Fusion; D030821:Plants, Genetically Modified / Q000166:cytology / Q000235:genetics / Q000378:metabolism; D021382:Protein Sorting Signals; D017434:Protein Structure, Tertiary; D021381:Protein Transport; D050765:Qa-SNARE Proteins / Q000235:genetics / Q000378:metabolism*; D011993:Recombinant Fusion Proteins / Q000235:genetics / Q000378:metabolism; D014617:Vacuoles / Q000378:metabolism
chemical_list: C489890:ATPEP12 protein, Arabidopsis; D029681:Arabidopsis Proteins; C097724:KNOLLE protein, Arabidopsis; D021382:Protein Sorting Signals; D050765:Qa-SNARE Proteins; D011993:Recombinant Fusion Proteins