JXB Advance Access published online on June 25, 2008
Journal of Experimental Botany, doi:10.1093/jxb/ern162
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RESEARCH PAPER |
The POK/AtVPS52 protein localizes to several distinct post-Golgi compartments in sporophytic and gametophytic cells
1INRA UR254, Station de Génétique et d'Amélioration des Plantes, Institut Jean-Pierre Bourgin, Centre de Versailles-Grignon, F-78026 Versailles, France
2Laboratoire de Dynamique de la Compartimentation Cellulaire, Institut des Sciences du Végétal, CNRS UPR2355, F-91198 Gif sur Yvette, France
3Department of Biological Sciences, University of Durham, South Road, Durham DH1 3LE, UK
* To whom correspondence should be addressed. E-mail: bonhomme{at}versailles.inra.fr
The organization and dynamics of the plant endomembrane system require both universal and plant-specific molecules and compartments. The latter, despite the growing wealth of information, remains poorly understood. From the study of an Arabidopsis thaliana male gametophytic mutant, it was possible to isolate a gene named POKY POLLEN TUBE (POK) essential for pollen tube tip growth. The similarity between the predicted POK protein sequence and yeast Vps52p, a subunit from the GARP/VFT complex which is involved in the docking of vesicles from the prevacuolar compartment to the Golgi apparatus, suggested that the POK protein plays a role in plant membrane trafficking. Genetic analysis of Arabidopsis mutants affecting AtVPS53 or AtVPS54 genes which encode putative POK partners shows a transmission defect through the male gametophyte for all lines, which is similar to the pok mutant. Using a combination of biochemical approaches and specific antiserum it has been demonstrated that the POK protein is present in phylogenetically divergent plant species, associated with membranes and belongs to a high molecular weight complex. Combination of immunolocalization studies and pharmacological approaches in different plant cells revealed that the POK protein associates with Golgi and post-Golgi compartments. The role of POK in post-Golgi endomembrane trafficking and as a member of a putative plant GARP/VFT complex is discussed.
Key words: Arabidopsis mutants, GARP/VFT complex, Golgi and post-Golgi compartments, pollen, pollen tube
Received 11 February 2008; Revised 28 March 2008 Accepted 13 May 2008