Glycosylinositol phosphorylceramides from Rosa cell cultures are boron-bridged in the plasma membrane and form complexes with rhamnogalacturonan II

Aline Voxeur, Stephen C. Fry*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract / Description of output

Boron (B) is essential for plant cell-wall structure and membrane functions. Compared with its role in cross-linking the pectic domain rhamnogalacturonan II (RG-II), little information is known about the biological role of B in membranes. Here, we investigated the involvement of glycosylinositol phosphorylceramides (GIPCs), major components of lipid rafts, in the membrane requirement for B. Using thin-layer chromatography and mass spectrometry, we first characterized GIPCs from Rosa cell culture. The major GIPC has one hexose residue, one hexuronic acid residue, inositol phosphate, and a ceramide moiety with a C18 trihydroxylated mono-unsaturated long-chain base and a C24 monohydroxylated saturated fatty acid. Disrupting B bridging (by B starvation in vivo or by treatment with cold dilute HCl or with excess borate in vitro) enhanced the GIPCs' extractability. As RG-II is the main B-binding site in plants, we investigated whether it could form a B-centred complex with GIPCs. Using high-voltage paper electrophoresis, we showed that addition of GIPCs decreased the electrophoretic mobility of radiolabelled RG-II, suggesting formation of a GIPC-B-RG-II complex. Last, using polyacrylamide gel electrophoresis, we showed that added GIPCs facilitate RG-II dimerization in vitro. We conclude that B plays a structural role in the plasma membrane. The disruption of membrane components by high borate may account for the phytotoxicity of excess B. Moreover, the in-vitro formation of a GIPC-B-RG-II complex gives the first molecular explanation of the wall-membrane attachment sites observed in vivo. Finally, our results suggest a role for GIPCs in the RG-II dimerization process.

Original languageEnglish
Pages (from-to)139-149
Number of pages11
JournalThe Plant Journal
Volume79
Issue number1
Early online date7 May 2014
DOIs
Publication statusPublished - 1 Jul 2014

Keywords / Materials (for Non-textual outputs)

  • boron
  • cell wall
  • cross-linking
  • glycosylinositol phosphoceramides
  • Rosa sp
  • lipid rafts
  • plasma membrane
  • rhamnogalacturonan II

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