Symmetric and Asymmetric Models for the Arabidopsis thaliana Plasma Membrane: A Simulation Study

Arabidopsis thaliana is an important model organism, which has attracted many biologists. While most research efforts have been on studying the genetics and proteins of this organism, a systematic study of its lipidomics is lacking. Here, we present a novel, asymmetric model of its cell membrane with its lipid composition consisting of five glycerophospholipids, two glycolipids, and sitosterol determined from multiple independent experiments. A typical lipid type in plant membranes is glycosyl inositol phosphoryl ceramide (GIPC), which accounts for about 10% of the total lipids in the outer leaflet in our model. Two symmetric models representing the inner and outer leaflets of the membrane were built and simulated until equilibrium was reached and then combined to form the asymmetric model. Our results indicate that the outer leaflet is more rigid and tightly packed compared to the inner leaflet. Pressure profiles for the two leaflets are overall similar though the outer leaflet exhibits larger oscillations. A special focus on lipid organization is discussed and the interplay between glycolipids and sitosterols is found to be important. The current model provides a baseline for future modeling of similar membranes and can be used to study partitioning of small molecules in the membrane or further developed to study the interaction between plant membrane proteins and lipids.