title: An Arabidopsis endo-1,4-beta-D-glucanase involved in cellulose synthesis undergoes regulated intracellular cycling.
abstract: The synthesis of cellulose microfibrils requires the presence of a membrane-bound endo-1,4-beta-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.
authors.affiliation: Laboratoire de Biologie Cellulaire, Institut Jean-Pierre Bourgin, Institut National de la Recherche Agronomique, Versailles, France.
authors.forename: Stéphanie
authors.initials: S
authors.lastname: Robert
authors.forename: Adeline
authors.initials: A
authors.lastname: Bichet
authors.forename: Olivier
authors.initials: O
authors.lastname: Grandjean
authors.forename: Daniel
authors.initials: D
authors.lastname: Kierzkowski
authors.forename: Béatrice
authors.initials: B
authors.lastname: Satiat-Jeunemaître
authors.forename: Sandra
authors.initials: S
authors.lastname: Pelletier
authors.forename: Marie-Theres
authors.initials: MT
authors.lastname: Hauser
authors.forename: Herman
authors.initials: H
authors.lastname: Höfte
authors.forename: Samantha
authors.initials: S
authors.lastname: Vernhettes
mesh_terms: D017360:Arabidopsis / Q000166:cytology / Q000201:enzymology*; D001483:Base Sequence; D002451:Cell Compartmentation; D002480:Cellulase / Q000378:metabolism*; D002482:Cellulose / Q000096:biosynthesis*; D017931:DNA Primers; D011992:Endosomes / Q000201:enzymology; D006056:Golgi Apparatus / Q000201:enzymology; D049452:Green Fluorescent Proteins / Q000378:metabolism; D018613:Microscopy, Confocal
chemical_list: D017931:DNA Primers; D049452:Green Fluorescent Proteins; D002482:Cellulose; D002480:Cellulase