Received July 18, 2005
Returned for revision September 14, 2005
Accepted October 13, 2005
An Arabidopsis Endo-1,4-
-D-Glucanase Involved in Cellulose Synthesis Undergoes Regulated Intracellular Cycling
Stéphanie Robert 1, Adeline Bichet 1, Olivier Grandjean 2, Daniel Kierzkowski 1, Béatrice Satiat-Jeunemaître 3, Sandra Pelletier 1, Marie-Theres Hauser 4, Herman Höfte 1, and Samantha Vernhettes 1*
1 Laboratoire de Biologie Cellulaire, Institut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, 78026 Versailles Cedex, France
2 Laboratoire Commun de Cytologie, Institut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, 78026 Versailles Cedex, France
3 Dynamique de la Compartimentation Cellulaire, Institut des Sciences du Végétal, Centre National de la Recherche Scientifique Unité Propre de Recherche 2355, 91198 Gif sur Yvette Cedex, France
4 Institute of Applied Genetics and Cell Biology, BOKU, University of Natural Resources and Applied Life Science, A-1190 Vienna, Austria
* To whom correspondence should be addressed. E-mail: samantha.vernhettes{at}versailles.inra.fr.
The synthesis of cellulose microfibrils requires the presence of a membrane-bound endo-1,4-
-D-glucanase, KORRIGAN1 (KOR1). Although the exact biochemical role of KOR1 in cellulose synthesis is unknown, we used the protein as a marker to explore the potential involvement of subcellular transport processes in cellulose synthesis. Using immunofluorescence and a green fluorescent protein (GFP)-KOR1 fusion that complemented the phenotype conferred by the kor1-1 mutant, we investigated the distribution of KOR1 in epidermal cells in the root meristem. KOR1 was localized in intracellular compartments corresponding to a heterogeneous population of organelles, which comprised the Golgi apparatus, FM4-64-labeled compartments referred to as early endosomes, and, in the case of GFP-KOR1, the tonoplast. Inhibition of cellulose synthesis by isoxaben promoted a net redistribution of GFP-KOR1 toward a homogeneous population of compartments, distinct from early endosomes, which were concentrated close to the plasma membrane facing the root surface. A redistribution of GFP-KOR1 away from early endosomes was also observed in the same cells at later stages of cell elongation. A subpopulation of GFP-KOR1-containing compartments followed trajectories along the plasma membrane, and this motility required intact microtubules. These observations demonstrate that the deposition of cellulose, like chitin synthesis in yeast, involves the regulated intracellular cycling of at least one enzyme required for its synthesis.
