Sphingolipid metabolism is strikingly different between pollen and leaf in Arabidopsis as revealed by compositional and gene expression profiling

Abstract

Although sphingolipids are essential for male gametophytic development in Arabidopsis thaliana, sphingolipid composition and biosynthetic gene expression have not been previously examined in pollen. In this report, electrospray ionization (ESI)-MS/MS was applied to characterization of sphingolipid compositional profiles in pollen isolated from wild type Arabidopsis Col-0 and a long-chain base (LCB) Δ4 desaturase mutant. Pollen fractions were highly enriched in glucosylceramides (GlcCer) relative to levels previously reported in leaves. Accompanying the loss of the Δ4 unsaturated LCB sphingadiene (d18:2) in the Δ4 desaturase mutant was a 50% reduction in GlcCer concentrations. In addition, pollen glycosylinositolphosphoceramides (GIPCs) were found to have a complex array of N-acetyl-glycosylated GIPCs, including species with up to three pentose units that were absent from leaf GIPCs. Underlying the distinct sphingolipid composition of pollen, genes for key biosynthetic enzymes for GlcCer and d18:2 synthesis and metabolism were more highly expressed in pollen than in leaves or seedlings, including genes for GlcCer synthase (GCS), sphingoid base C-4 hydroxylase 2 (SBH2), LCB Δ8 desaturases (SLD1 and SLD2), and LOH2 ceramide synthase (LOH2). Overall, these findings indicate strikingly divergent sphingolipid metabolism between pollen and leaves in Arabidopsis, the significance of which remains to be determined.

GIPC: Glycosyl Inositol Phospho Ceramides, the major sphingolipids on earth

“…15 The significance of this remains to be determined. We recently showed that GIPCs are the major lipids of the tobacco (Nicotiana tabacum) highly-purified PM, and can reach up to 40 mol% of total lipids, whereas gangliosides represent only few percent of animal PM, e.g.…”

Molecular characterization and targeted quantitative profiling of the sphingolipidome in rice

“…The emerging lipid metabolomic approach called lipidomics is a powerful tool to demonstrate dynamics of lipid metabolism and to identify new lipid classes associated with various biological functions (Retra et al ., ; Burgos et al ., ; Degenkolbe et al ., ; Liu et al ., ; Okazaki et al ., , ; Vu et al ., ), whereas GIPC species have remained insufficiently or not detected due to their poor recovery in the solvent systems optimized for glycerolipid extraction. However, recent analytical advances focusing on sphingolipids have been yielding comprehensive sphingolipid profiles, especially in Arabidopsis and other dicotyledonous plants (Markham et al ., ; Markham and Jaworski, ; Chen et al ., 2008; Wang et al ., ; Chen et al ., 2011; Markham et al ., ; Kimberlin et al ., ; Nagano et al ., ; Luttgeharm et al ., ). Sphingolipid structures are estimated to vary among different plant tissues and species (Markham et al ., ; Buré et al ., , ; Blaas and Humpf, ; Cacas et al ., ; Tellier et al ., ), but sphingolipidomic profiles in monocots remain to be addressed.…”

Loss of Inositol Phosphorylceramide Sphingolipid Mannosylation Induces Plant Immune Responses and Reduces Cellulose Content in Arabidopsis

“…In most Arabidopsis tissues, the major GIPC glycosylation consists of one hexose (Hex) attached to GlcA linked to IPC (Hex-GlcA-IPC), while in seeds, the dominant GIPC contains an amino sugar linked to the GlcA (Tellier et al, 2014). A recent report found that Arabidopsis pollen GIPCs also have a different glycosylation pattern, consisting of a complex array of N-acetyl-glycosylated GIPCs, including species with up to three pentose units (Luttgeharm et al, 2015). Other plant tissues, such as tobacco (Nicotiana tabacum) leaves, do not contain the Hex-GlcA-IPC found in Arabidopsis but instead the dominant structure consists of GlcNAc attached to the GlcA linked to IPC (Carter et al, 1958;Kaul and Lester, 1975;Hsieh et al, 1981;Buré et al, 2011).…”