title: Abnormal glycosphingolipid mannosylation triggers salicylic acid-mediated responses in Arabidopsis.
abstract: The Arabidopsis thaliana protein GOLGI-LOCALIZED NUCLEOTIDE SUGAR TRANSPORTER (GONST1) has been previously identified as a GDP-d-mannose transporter. It has been hypothesized that GONST1 provides precursors for the synthesis of cell wall polysaccharides, such as glucomannan. Here, we show that in vitro GONST1 can transport all four plant GDP-sugars. However, gonst1 mutants have no reduction in glucomannan quantity and show no detectable alterations in other cell wall polysaccharides. By contrast, we show that a class of glycosylated sphingolipids (glycosylinositol phosphoceramides [GIPCs]) contains Man and that this mannosylation is affected in gonst1. GONST1 therefore is a Golgi GDP-sugar transporter that specifically supplies GDP-Man to the Golgi lumen for GIPC synthesis. gonst1 plants have a dwarfed phenotype and a constitutive hypersensitive response with elevated salicylic acid levels. This suggests an unexpected role for GIPC sugar decorations in sphingolipid function and plant defense signaling. Additionally, we discuss these data in the context of substrate channeling within the Golgi.
authors.affiliation: Department of Biochemistry, University of Cambridge, Cambridge CB2 1QW, United Kingdom.
authors.forename: Jenny C
authors.initials: JC
authors.lastname: Mortimer
authors.forename: Xiaolan
authors.initials: X
authors.lastname: Yu
authors.forename: Sandra
authors.initials: S
authors.lastname: Albrecht
authors.forename: Francesca
authors.initials: F
authors.lastname: Sicilia
authors.forename: Mariela
authors.initials: M
authors.lastname: Huichalaf
authors.forename: Diego
authors.initials: D
authors.lastname: Ampuero
authors.forename: Louise V
authors.initials: LV
authors.lastname: Michaelson
authors.forename: Alex M
authors.initials: AM
authors.lastname: Murphy
authors.forename: Toshiro
authors.initials: T
authors.lastname: Matsunaga
authors.forename: Samantha
authors.initials: S
authors.lastname: Kurz
authors.forename: Elaine
authors.initials: E
authors.lastname: Stephens
authors.forename: Timothy C
authors.initials: TC
authors.lastname: Baldwin
authors.forename: Tadashi
authors.initials: T
authors.lastname: Ishii
authors.forename: Johnathan A
authors.initials: JA
authors.lastname: Napier
authors.forename: Andreas P M
authors.initials: AP
authors.lastname: Weber
authors.forename: Michael G
authors.initials: MG
authors.lastname: Handford
authors.forename: Paul
authors.initials: P
authors.lastname: Dupree
mesh_terms: D017360:Arabidopsis / Q000235:genetics / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics / Q000378:metabolism*; D001692:Biological Transport / Q000235:genetics; D002473:Cell Wall / Q000235:genetics / Q000378:metabolism; D006028:Glycosphingolipids / Q000378:metabolism*; D006031:Glycosylation; D006056:Golgi Apparatus / Q000378:metabolism; D006154:Guanosine Diphosphate Fucose / Q000378:metabolism; D006155:Guanosine Diphosphate Mannose / Q000378:metabolism; D006156:Guanosine Diphosphate Sugars / Q000378:metabolism; D015151:Immunoblotting; D008358:Mannose / Q000378:metabolism*; D026901:Membrane Transport Proteins / Q000235:genetics / Q000378:metabolism*; D008856:Microscopy, Fluorescence; D009154:Mutation; D020156:Salicylic Acid / Q000378:metabolism*
chemical_list: D029681:Arabidopsis Proteins; C445096:GONST1 protein, Arabidopsis; D006028:Glycosphingolipids; D006156:Guanosine Diphosphate Sugars; D026901:Membrane Transport Proteins; D006154:Guanosine Diphosphate Fucose; D006155:Guanosine Diphosphate Mannose; C100085:guanosine diphosphate glucose; D020156:Salicylic Acid; D008358:Mannose