Plant PM is an essential barrier between the cell and the external environment. PM is stable but adaptable, crucial for signal perception and transmission. It consists of a asymmetrical lipid bilayer made up of three different classes of lipid: sphingolipids, sterols and phospholipids.
The most abundant sphingolipid in plant PM is Glycosyl InositoPhosphoryl Ceramide (GIPC) representing up to 40-50% of total sphingolipids in plants. GIPCs are assumed to be almost exclusively in the outer leaflet of the PM. In this study, we investigate the structure of GIPC and its role in membrane organization. Since GIPCs are not commercially available, we develop a protocol to extract and isolate GIPC-enriched fractions from eudicots (cauliflower and tobacco) and monocots (leek and rice). Lipidomic analysis confirmed the presence of different GIPC series containing mostly h24/t18:1 as the most abundant ceramide. The glycan head groups of the different GIPC series from monocots and dicots were analyzed showing different sugar components.
Biophysics tools such as Langmuir, AFM, solid state NMR, and molecular modelling were used to investigate the physical properties of GIPC and its interaction with free and conjugated phytosterols. We demonstrate the importance of molecular structure in these interactions. We showed that GIPC increases the thickness and electronegativity of model membrane through different complementary approaches.