Biochemical survey of the polar head of plant glycosylinositolphosphoceramides unravels broad diversity

Abstract

Although Glycosyl-Inositol-Phospho-Ceramides (GIPCs) are the main sphingolipids of plant tissues, they remain poorly characterized in term of structures. This lack of information, notably with regard to polar heads, currently hampers the understanding of GIPC functions in biological systems. This situation prompted us to undertake a large scale-analysis of plant GIPCs: 23 plant species chosen in various phylogenetic groups were surveyed for their total GIPC content. GIPCs were extracted and their polar heads were characterized by negative ion MALDI and ESI mass spectrometry. Our data shed light on an unexpected broad diversity of GIPC distributions within Plantae, and the occurrence of yet-unreported GIPC structures in green and red algae. In monocots, GIPCs with three saccharides were apparently found to be major, whereas a series with two saccharides was dominant in Eudicots within a few notable exceptions. In plant cell cultures, GIPC polar heads appeared to bear a higher number of glycan units than in the tissue from which they originate. Perspectives are discussed in term of GIPC metabolism diversity and function of these lipids.

Keywords: 2,6-dihydroxy-acetophenone; Berries; DHA; ESI; FA; GIPC; Gal; GlcA; GlcN; Glycosphingolipid; Glycosyl-Inositol-Phospho-Ceramide; Hex; IPC; LCB; LCFA; MALDI-MS; MALDI-TOF; MS/MS; Mass spectrometry; N-Ac; N-acetyl; Pen; Photosynthetic tissues; Polar head; Roots; VLFCA; electrospray ionization; fatty acid; galactose; glucosamine; glucuronic acid; hVLCFA; hexose; hydroxylated VLCFA; inositol-phosphoceramide; long-chain base; long-chain fatty acid; matrix assisted laser desorption-ionization-mass spectrometry; pentose; tandem mass spectrometry; very long-chain fatty acid.