title: Glycosylation of inositol phosphorylceramide sphingolipids is required for normal growth and reproduction in Arabidopsis.
abstract: Sphingolipids are a major component of plant plasma membranes and endomembranes, and mediate a diverse range of biological processes. Study of the highly glycosylated glycosyl inositol phosphorylceramide (GIPC) sphingolipids has been slow as a result of challenges associated with the extractability of GIPCs, and their functions in the plant remain poorly characterized. We recently discovered an Arabidopsis GIPC glucuronosyltransferase, INOSITOL PHOSPHORYLCERAMIDE GLUCURONOSYLTRANSFERASE 1 (IPUT1), which is the first enzyme in the GIPC glycosylation pathway. Plants homozygous for the iput1 loss-of-function mutation were unobtainable, and so the developmental effects of reduced GIPC glucuronosylation could not be analyzed in planta. Using a pollen-specific rescue construct, we have here isolated homozygous iput1 mutants. The iput1 mutants show severe dwarfism, compromised pollen tube guidance, and constitutive activation of salicyclic acid-mediated defense pathways. The mutants also possess reduced GIPCs, increased ceramides, and an increased incorporation of short-chain fatty acids and dihydroxylated bases into inositol phosphorylceramides and GIPCs. The assignment of a direct role for GIPC glycan head groups in the impaired processes in iput1 mutants is complicated by the vast compensatory changes in the sphingolipidome; however, our results reveal that the glycosylation steps of GIPC biosynthesis are important regulated components of sphingolipid metabolism. This study corroborates previously suggested roles for GIPC glycans in plant growth and defense, suggests important roles for them in reproduction and demonstrates that the entire sphingolipidome is sensitive to their status.
authors.affiliation: Joint BioEnergy Institute, Emeryville, CA, 94608, USA.|Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
authors.forename: Virginia
authors.initials: V
authors.lastname: Tartaglio
authors.affiliation: Joint BioEnergy Institute, Emeryville, CA, 94608, USA.|Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.|Center for Plant Science Innovation and Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA.
authors.forename: Emilie A
authors.initials: EA
authors.lastname: Rennie
authors.affiliation: Center for Plant Science Innovation and Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA.
authors.forename: Rebecca
authors.initials: R
authors.lastname: Cahoon
authors.affiliation: Joint BioEnergy Institute, Emeryville, CA, 94608, USA.|Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
authors.forename: George
authors.initials: G
authors.lastname: Wang
authors.affiliation: Joint BioEnergy Institute, Emeryville, CA, 94608, USA.|Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
authors.forename: Edward
authors.initials: E
authors.lastname: Baidoo
authors.affiliation: Joint BioEnergy Institute, Emeryville, CA, 94608, USA.|Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.
authors.forename: Jennifer C
authors.identifier: 0000-0001-6624-636X
authors.initials: JC
authors.lastname: Mortimer
authors.affiliation: Center for Plant Science Innovation and Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE, 68588, USA.
authors.forename: Edgar B
authors.initials: EB
authors.lastname: Cahoon
authors.affiliation: Joint BioEnergy Institute, Emeryville, CA, 94608, USA.|Biological Systems and Engineering Division, Lawrence Berkeley National Laboratory, Berkeley, CA, 94720, USA.|Department of Plant and Microbial Biology, University of California, Berkeley, CA, 94720, USA.
authors.forename: Henrik V
authors.identifier: 0000-0002-6702-3560
authors.initials: HV
authors.lastname: Scheller
mesh_terms: D017360:Arabidopsis / Q000254:growth & development* / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000235:genetics* / Q000378:metabolism; D014453:Glucuronosyltransferase / Q000235:genetics* / Q000378:metabolism; D006028:Glycosphingolipids / Q000378:metabolism*; D006031:Glycosylation; D006720:Homozygote; D009154:Mutation; D030821:Plants, Genetically Modified; D011058:Pollen / Q000235:genetics; D053205:Pollen Tube / Q000235:genetics / Q000378:metabolism; D013107:Sphingolipids / Q000378:metabolism
chemical_list: D029681:Arabidopsis Proteins; D006028:Glycosphingolipids; D013107:Sphingolipids; C477937:inositolphosphorylceramide; D014453:Glucuronosyltransferase; C000598949:IPUT1 protein, Arabidopsis
keywords: 
  Arabidopsis thaliana
  ; IPUT1; glucuronosyltransferase; glycosyl inositol phosphorylceramides; pollen tube growth; sphingolipid