Fatty acid profiles from the plasma membrane and detergent resistant membranes of two plant species

Membrane microdomains: Structural and signaling platforms for establishing membrane polarity

Cell polarity results from the asymmetric distribution of cellular structures, molecules, and functions. Polarity is a fundamental cellular trait that can determine the orientation of cell division, the formation of particular cell shapes, and ultimately the development of a multicellular body. To maintain the distinct asymmetric distribution of proteins and lipids in cellular membranes, plant cells have developed complex trafficking and regulatory mechanisms. Major advances have been made in our understanding of how membrane microdomains influence the asymmetric distribution of proteins and lipids. In this review, we first give an overview of cell polarity. Next, we discuss current knowledge concerning membrane microdomains and their roles as structural and signaling platforms to establish and maintain membrane polarity, with a special focus on the asymmetric distribution of proteins and lipids, and advanced microscopy techniques to observe and characterize membrane microdomains. Finally, we review recent advances regarding membrane trafficking in cell polarity establishment and how the balance between exocytosis and endocytosis affects membrane polarity.

Sphingolipid Effects on the Plasma Membrane Produced by Addition of Fumonisin B1 to Maize Embryos

Fumonisin B1 is a mycotoxin produced by Fusarium verticillioides that modifies the membrane properties from animal cells and inhibits complex sphingolipids synthesis through the inhibition of ceramide synthase. The aim of this work was to determine the effect of Fumonisin B1 on the plant plasma membrane when the mycotoxin was added to germinating maize embryos. Fumonisin B1 addition to the embryos diminished plasma membrane fluidity, increased electrolyte leakage, caused a 7-fold increase of sphinganine and a small decrease in glucosylceramide in the plasma membrane, without affecting phytosphingosine levels or fatty acid composition. A 20%-30% inhibition of the plasma membrane H+-ATPase activity was observed when embryos were germinated in the presence of the mycotoxin. Such inhibition was only associated to the decrease in glucosylceramide and the addition of exogenous ceramide to the embryos relieved the inhibition of Fumonisin B1. These results indicate that exposure of the maize embryos for 24 h to Fumonisin B1 allowed the mycotoxin to target ceramide synthase at the endoplasmic reticulum, eliciting an imbalance of endogenous sphingolipids. The latter disrupted membrane properties and inhibited the plasma membrane H+-ATPase activity. Altogether, these results illustrate the mode of action of the pathogen and a plant defense strategy.

Plant lipids: Key players of plasma membrane organization and function

The plasma membrane (PM) is the biological membrane that separates the interior of all cells from the outside. The PM is constituted of a huge diversity of proteins and lipids. In this review, we will update the diversity of molecular species of lipids found in plant PM. We will further discuss how lipids govern global properties of the plant PM, explaining that plant lipids are unevenly distributed and are able to organize PM in domains. From that observation, it emerges a complex picture showing a spatial and multiscale segregation of PM components. Finally, we will discuss how lipids are key players in the function of PM in plants, with a particular focus on plant-microbe interaction, transport and hormone signaling, abiotic stress responses, plasmodesmata function. The last chapter is dedicated to the methods that the plant membrane biology community needs to develop to get a comprehensive understanding of membrane organization in plants.

Lipid profiles of detergent resistant fractions of the plasma membrane in oat and rye in association with cold acclimation and freezing tolerance

Cold acclimation (CA) results in alteration of the plasma membrane (PM) lipid composition in plants, which plays a crucial role in the acquisition of freezing tolerance via membrane stabilization. Recent studies have indicated that PM structure is consistent with the fluid mosaic model but is laterally non-homogenous and contains microdomains enriched in sterols, sphingolipids and specific proteins. In plant cells, the function of these microdomains in relation to CA and freezing tolerance is not yet fully understood. The present study aimed to investigate the lipid compositions of detergent resistant fractions of the PM (DRM) which are considered to represent microdomains. They were prepared from leaves of low-freezing tolerant oat and high-freezing tolerant rye. The DRMs contained higher proportions of sterols, sphingolipids and saturated phospholipids than the PM. In particular, one of the sterol lipid classes, acylated sterylglycoside, was the predominant sterol in oat DRM while rye DRM contained free sterol as the major sterol. Oat and rye showed different patterns (or changes) of sterols and 2-hydroxy fatty acids of sphingolipids of DRM lipids during CA. Taken together, these results suggest that CA-induced changes of lipid classes and molecular species in DRMs are associated with changes in the thermodynamic properties and physiological functions of microdomains during CA and hence, influence plant freezing tolerance.

Plant lipid environment and membrane enzymes: the case of the plasma membrane H+-ATPase

Several lipid classes constitute the universal matrix of the biological membranes. With their amphipathic nature, lipids not only build the continuous barrier that confers identity to every cell and organelle, but they are also active actors that modulate the activity of the proteins immersed in the lipid bilayer. The plasma membrane H(+)-ATPase, an enzyme from plant cells, is an excellent example of a transmembrane protein whose activity is influenced by the hydrophilic compartments at both sides of the membrane and by the hydrophobic domains of the lipid bilayer. As a result, an extensive documentation of the effect of numerous amphiphiles in the enzyme activity can be found. Detergents, membrane glycerolipids, and sterols can produce activation or inhibition of the enzyme activity. In some cases, these effects are associated with the lipids of the membrane bulk, but in others, a direct interaction of the lipid with the protein is involved. This review gives an account of reports related to the action of the membrane lipids on the H(+)-ATPase activity.