title: KATAMARI1/MURUS3 Is a novel golgi membrane protein that is required for endomembrane organization in Arabidopsis.
abstract: In plant cells, unlike animal and yeast cells, endomembrane dynamics appear to depend more on actin filaments than on microtubules. However, the molecular mechanisms of endomembrane-actin filament interactions are unknown. In this study, we isolated and characterized an Arabidopsis thaliana mutant, katamari1 (kam1), which has a defect in the organization of endomembranes and actin filaments. The kam1 plants form abnormally large aggregates that consist of endoplasmic reticulum with actin filaments in the perinuclear region within the cells and are defective in normal cell elongation. Map-based cloning revealed that the KAM1 gene is allelic to the MUR3 gene. We demonstrate that the KAM1/MUR3 protein is a type II membrane protein composed of a short cytosolic N-terminal domain and a transmembrane domain followed by a large lumenal domain and is localized specifically on Golgi membranes. We further show that actin filaments interact with Golgi stacks via KAM1/MUR3 to maintain the proper organization of endomembranes. Our results provide functional evidence that KAM1/MUR3 is a novel component of the Golgi-mediated organization of actin functioning in proper endomembrane organization and cell elongation.
authors.affiliation: Department of Botany, Graduate School of Science, Kyoto University, Kyoto 606-8502, Japan.
authors.forename: Kentaro
authors.initials: K
authors.lastname: Tamura
authors.forename: Tomoo
authors.initials: T
authors.lastname: Shimada
authors.forename: Maki
authors.initials: M
authors.lastname: Kondo
authors.forename: Mikio
authors.initials: M
authors.lastname: Nishimura
authors.forename: Ikuko
authors.initials: I
authors.lastname: Hara-Nishimura
mesh_terms: D008841:Actin Cytoskeleton / Q000378:metabolism / Q000648:ultrastructure; D017360:Arabidopsis / Q000378:metabolism* / Q000648:ultrastructure; D049108:Cell Enlargement; D048430:Cell Shape; D005700:Galactosyltransferases / Q000235:genetics / Q000378:metabolism*; D006056:Golgi Apparatus / Q000378:metabolism* / Q000648:ultrastructure; D007425:Intracellular Membranes / Q000378:metabolism* / Q000648:ultrastructure; D008565:Membrane Proteins / Q000235:genetics / Q000378:metabolism*; D009154:Mutation / Q000235:genetics; D015388:Organelles / Q000378:metabolism / Q000648:ultrastructure
chemical_list: D008565:Membrane Proteins; D005700:Galactosyltransferases; C478982:MUR3 protein, Arabidopsis