Plastoglobule

Plastoglobule is a small, lipoprotein particle located in plastids, particularly chloroplasts, and is often associated with thylakoid membranes. Plastoglobules are bounded by a single lipid monolayer and contain a hydrophobic core of neutral lipids, with proteins embedded in or attached to the monolayer. They are dynamic structures whose size and abundance change with development and environmental conditions.

The lipid phase includes neutral lipids such as triacylglycerols and various esters, along with isoprenoid-derived compounds such as tocopherols (vitamin E), plastoquinone, plastochinones, and carotenoids. The protein phase features plastoglobulins (PGL1–PGL4), fibrillins, and enzymes involved in lipid and isoprenoid metabolism, including lipases and ABC1-like kinases (ABC1K1–ABC1K5) associated with plastoglobules.

Functions of plastoglobules are diverse. They participate in lipid remodeling and storage within plastids and serve as reservoirs for isoprenoids that protect photosystems from oxidative stress. They contribute to thylakoid membrane repair during light stress and senescence and play roles in plastid development and pigment metabolism, including carotenoid and plastoquinone biosynthesis. Their activity links lipid homeostasis to photosynthetic performance and stress responses.

Plastoglobules are present in the chloroplasts of plants and many algae, and also in chromoplasts and other plastids. Their number and size increase during aging, stress, and fruit ripening. Research on plastoglobules informs understanding of vitamin E and carotenoid metabolism, plastid lipid remodeling, and plant stress tolerance.