Revisiting Plant Plasma Membrane Lipids in Tobacco: A Focus on Sphingolipids

Abstract

The lipid composition of plasma membrane (PM) and the corresponding detergent-insoluble membrane (DIM) fraction were analyzed with a specific focus on highly polar sphingolipids, so-called glycosyl inositol phosphorylceramides (GIPCs). Using tobacco (Nicotiana tabacum) 'Bright Yellow 2' cell suspension and leaves, evidence is provided that GIPCs represent up to 40 mol % of the PM lipids. Comparative analysis of DIMs with the PM showed an enrichment of 2-hydroxylated very-long-chain fatty acid-containing GIPCs and polyglycosylated GIPCs in the DIMs. Purified antibodies raised against these GIPCs were further used for immunogold-electron microscopy strategy, revealing the distribution of polyglycosylated GIPCs in domains of 35 6 7 nm in the plane of the PM. Biophysical studies also showed strong interactions between GIPCs and sterols and suggested a role for very-long-chain fatty acids in the interdigitation between the two PM-composing monolayers. The ins and outs of lipid asymmetry, raft formation, and interdigitation in plant membrane biology are finally discussed.Eukaryotic plasma membranes (PMs) are composed of three main classes of lipids, glycerolipids, sphingolipids, and sterols, which may account for up to 100,000 different molecular species (Yetukuri et al., 2008;Shevchenko and Simons, 2010). Overall, all glycerolipids share the same molecular moieties in plants, animals, and fungi. By contrast, sterols and sphingolipids are different and specific to each kingdom. For instance, the plant PM contains an important number of sterols, among which b-sitosterol, stigmasterol, and campesterol predominate (Furt et al., 2011). In addition to free sterols, phytosterols can be conjugated to form steryl glycosides (SG) and acyl steryl glycosides (ASG) that represent up to approximately 15% of the tobacco (Nicotiana tabacum) PM (Furt et al., 2010). As for sphingolipids, sphingomyelin, the major phosphosphingolipid in animals, which harbors a phosphocholine as a polar head, is not detected in plants. Glycosyl

Plasma Membrane Microdomains Are Essential for Rac1-RbohB/H-Mediated Immunity in Rice

“…In addition, in vivo visualization of PM order using di-4-ANEPPDHQ demonstrated that the heterogeneity of the rice cell PM was lower in OsFAH1/2-KD1 than in the wild type. Furthermore, Cacas et al (2016) recently confirmed the enrichment of hGIPCs in DRMs of tobacco (Nicotiana tabacum) cells. Therefore, hydroxyl groups in 2-hydroxy sphingolipids are likely to be important for the organization of PM microdomains in rice cells.…”

“…In plants, lipid analyses confirm the accumulation of sphingolipids, especially GlcCers and GIPCs, and sterols in PM microdomains (Lefebvre et al, 2007;Laloi et al, 2007;Cacas et al, 2016). In addition, depletion of sterols by treatment with agents such as MbCD and filipin has a severe effect not only on formation of PM microdomains, but also on microdomain protein composition and physiological functions including pollen tube tip growth and abscisic acid signaling (Roche et al, 2008;Kierszniowska et al, 2009;Liu et al, 2009;Demir et al, 2013).…”

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

“…0.6% of total brain lipids! 16,17 Polyglycosylated GIPCs and polyphosphoinositides cluster within nanodomains in plant PM…”

ORM Expression Alters Sphingolipid Homeostasis and Differentially Affects Ceramide Synthase Activities

“…Sphingolipids play critical roles in plant growth and development as essential components of endomembranes, including the plasma membrane, where they constitute more than 40% of the total lipid (Sperling et al, 2005;Cacas et al, 2016). Sphingolipids also are highly enriched in detergent-insoluble membrane fractions of the plasma membrane that form microdomains for proteins with important cell surface activities, including cell wall biosynthesis and hormone transport (Cacas et al, , 2016Perraki et al, 2012;Bayer et al, 2014).…”

“…Sphingolipids also are highly enriched in detergent-insoluble membrane fractions of the plasma membrane that form microdomains for proteins with important cell surface activities, including cell wall biosynthesis and hormone transport (Cacas et al, , 2016Perraki et al, 2012;Bayer et al, 2014). In addition, sphingolipids, particularly those with very-long-chain fatty acids (VLCFAs), are integrally associated with Golgi-mediated protein trafficking that underlies processes related to the growth of plant cells (Bach et al, 2008(Bach et al, , 2011Markham et al, 2011;Melser et al, 2011).…”