GLUCOSAMINE INOSITOLPHOSPHORYLCERAMIDE TRANSFERASE1 (GINT1) Is a GlcNAc-Containing Glycosylinositol Phosphorylceramide Glycosyltransferase

Abstract

Glycosylinositol phosphorylceramides (GIPCs), which have a ceramide core linked to a glycan headgroup of varying structures, are the major sphingolipids in the plant plasma membrane. Recently, we identified the major biosynthetic genes for GIPC glycosylation in Arabidopsis () and demonstrated that the glycan headgroup is essential for plant viability. However, the function of GIPCs and the significance of their structural variation are poorly understood. Here, we characterized the Arabidopsis glycosyltransferase GLUCOSAMINE INOSITOLPHOSPHORYLCERAMIDE TRANSFERASE1 (GINT1) and showed that it is responsible for the glycosylation of a subgroup of GIPCs found in seeds and pollen that contain GlcNAc and GlcN [collectively GlcN(Ac)]. In Arabidopsis plants, loss of the GlcN(Ac) GIPCs did not affect vegetative growth, although seed germination was less sensitive to abiotic stress than in wild-type plants. However, in rice, where GlcN(Ac) containing GIPCs are the major GIPC subgroup in vegetative tissue, loss of GINT1 was seedling lethal. Furthermore, we could produce, de novo, "rice-like" GlcN(Ac) GIPCs in Arabidopsis leaves, which allowed us to test the function of different sugars in the GIPC headgroup. This study describes a monocot GIPC biosynthetic enzyme and shows that its Arabidopsis homolog has the same biochemical function. We also identify a possible role for GIPCs in maintaining cell-cell adhesion.

Sphingolipids: towards an integrated view of metabolism during the plant stress response

“…Based on work performed in yeast where 3-ketosphinganine reductase suppressed Ca 2+ sensitivity (Beeler et al, 1998), the authors hypothesised that KDSR acts as a suppressor of the calcium signal during salt stress. Seeds of Atgint1 (glucosamine inositol phosphorylceramide trans-ferase1, responsible for the glycosylation of some GIPCs) mutants displayed a higher germination rate than WT in response to salt stress, although this difference disappeared at higher salt concentrations (Ishikawa et al, 2018). The Atacer mutant and AtACER RNAi lines displayed high ceramide levels but reduced LCBs due to a disruption of an alkaline ceramidase gene (Wu et al, 2015a).…”

Plant-Unique cis/trans Isomerism of Long-Chain Base Unsaturation is Selectively Required for Aluminum Tolerance Resulting from Glucosylceramide-Dependent Plasma Membrane Fluidity

“…Total sphingolipids were prepared from lyophilized rice tissues and quantified by LC-MS/MS as described previously [25,48]. The lipid content was represented as nmol per g dry weight (DW).…”

Purification, characterization and influence on membrane properties of the plant-specific sphingolipids GIPC

“…GIPCs, although one of the fundamental components of the plant PM model have been poorly studied, in part due to the absence of commercial preparations. Recent evidence has demonstrated that a loss of the glycosylation is lethal, (Ishikawa et al, 2018) (Rennie et al, 2014), and that misglycosylation affects both abiotic and biotic stress responses, as reviewed in (Mortimer & Scheller, 2020).…”