title: The timely deposition of callose is essential for cytokinesis in Arabidopsis.
abstract: The primary plant cell wall is laid down over a brief period of time during cytokinesis. Initially, a membrane network forms at the equator of a dividing cell. The cross-wall is then assembled and remodeled within this membrane compartment. Callose is the predominant luminal component of the nascent cross-wall or cell plate, but is not a component of intact mature cell walls, which are composed primarily of cellulose, pectins and xyloglucans. Widely accepted models postulate that callose comprises a transient, rapid spreading force for the expansion of membrane networks during cytokinesis. In this study, we clone and characterize an Arabidopsis gene, MASSUE/AtGSL8, which encodes a putative callose synthase. massue mutants are seedling-lethal and have a striking cytokinesis-defective phenotype. Callose deposition was delayed in the cell plates of massue mutants. Mutant cells were occasionally bi- or multi-nucleate, with cell-wall stubs, and we frequently observed gaps at the junction between cross-walls and parental cell walls. The results suggest that the timely deposition of callose is essential for the completion of plant cytokinesis. Surprisingly, confocal analysis revealed that the cell-plate membrane compartment forms and expands, seemingly as far as the parental wall, prior to the appearance of callose. We discuss the possibility that callose may be required to establish a lasting connection between the nascent cross-wall and the parental cell wall.
authors.affiliation: Technische Universität München, Botanik, Am Hochanger 4, D-85354 Freising, Germany.
authors.forename: Knut
authors.initials: K
authors.lastname: Thiele
authors.forename: Gerhard
authors.initials: G
authors.lastname: Wanner
authors.forename: Viktoria
authors.initials: V
authors.lastname: Kindzierski
authors.forename: Gerd
authors.initials: G
authors.lastname: Jürgens
authors.forename: Ulrike
authors.initials: U
authors.lastname: Mayer
authors.forename: Fiona
authors.initials: F
authors.lastname: Pachl
authors.forename: Farhah F
authors.initials: FF
authors.lastname: Assaad
mesh_terms: D000483:Alleles; D017360:Arabidopsis / Q000166:cytology* / Q000235:genetics / Q000378:metabolism; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism; D032461:Chromosomes, Plant; D003001:Cloning, Molecular; D048749:Cytokinesis; D017343:Genes, Plant; D005936:Glucans / Q000235:genetics / Q000378:metabolism*; D005964:Glucosyltransferases / Q000235:genetics / Q000378:metabolism; D018613:Microscopy, Confocal; D008938:Mitosis; D010368:Pectins / Q000235:genetics / Q000378:metabolism; D010641:Phenotype; D018517:Plant Roots / Q000378:metabolism / Q000648:ultrastructure; D036226:Seedlings / Q000378:metabolism / Q000648:ultrastructure; D012639:Seeds / Q000378:metabolism / Q000648:ultrastructure; D013997:Time Factors; D014990:Xylans / Q000235:genetics / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D005936:Glucans; D014990:Xylans; C029353:xyloglucan; D010368:Pectins; C048306:callose; D005964:Glucosyltransferases; C549616:chorus protein, Arabidopsis; C020570:1,3-beta-glucan synthase