Present address: Regierung von Oberbayern, Technischer Umweltschutz – Gentechnik, Maximilianstraße 39, 80538 München, Germany.
Functional anatomy of the Arabidopsis cytokinesis-specific syntaxin KNOLLE
Article first published online: 19 SEP 2011
© 2011 The Authors. The Plant Journal © 2011 Blackwell Publishing Ltd
The Plant Journal
Volume 68, Issue 5, pages 755–764, December 2011
How to Cite
Touihri, S., Knöll, C., Stierhof, Y.-D., Müller, I., Mayer, U. and Jürgens, G. (2011), Functional anatomy of the Arabidopsis cytokinesis-specific syntaxin KNOLLE. The Plant Journal, 68: 755–764. doi: 10.1111/j.1365-313X.2011.04736.x
- Issue published online: 25 NOV 2011
- Article first published online: 19 SEP 2011
- Accepted manuscript online: 12 AUG 2011 02:07PM EST
- Received 10 May 2011; revised 19 July 2011; accepted 3 August 2011; published online 19 September 2011.
- membrane traffic;
- chimeric protein;
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 (KNΔ1–82) had the same effect as its presence in the chimeric protein (KN1–82-PEP1264–279), 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.