Lipid droplets (LD) are intracellular organelles that are essential for energy storage and lipid metabolism. They usually consist of an oil core coated with a single layer of phospholipids and proteins (such as oleosin). However, the details of the mechanism of LD biogenesis are still unclear.
On September 22, 2021, Nature Communication published an online research paper entitled "Sterols are required for the coordinated assembly of lipid droplets in developing seeds" from the Changcheng Xu group of Brookhaven National Laboratory in the United States. The study revealed the role of sterols/sterols in coordinating the synthesis of oil and oleosin and their assembly into lipid droplets (LDs), highlighting the importance of membrane lipids in regulating LD biogenesis.
Sterols are lipids derived from isoprenoids and play important roles in cell structure, function, and physiology. As an important part of biological membranes, sterols interact with phospholipids and proteins in the membrane to regulate membrane fluidity, permeability and membrane protein function. In addition to their structural role, sterols are also metabolic precursors of brassinosteroids (BRs). In addition, some sterols and sterol biosynthetic intermediates have been revealed to function as signal molecules that affect transcription and signal transduction pathways.
Phytosterols synthesize cycloartenol from acetyl-CoA via the mevalonate pathway in the endoplasmic reticulum. Cycloartenol (cycloartenol) is a common substrate for the synthesis of cholesterol, minor sterols in plants, and major sterols, sitosterol, stigmasterol and campesterol. The conversion of cycloartenol to major phytosterols involves a series of enzymatic reactions, including methylation, demethylation, reduction, isomerization and desaturation (as shown in the figure below). The physical structure of LD consists of a hydrophobic core of sterol esters and tricyclic glycerols (TAGs), surrounded by a monolayer of phospholipids and free sterols, which contains a small group of embedded or peripherally bound proteins. At present, the exact mechanism details of LD biogenesis are still poorly understood.