Plastoglobuli

Plastoglobuli are discrete lipid-containing bodies located inside plastids, most notably chloroplasts and chromoplasts. They are closely associated with thylakoid membranes and are bounded by a small, continuous monolayer of lipids derived from the plastid envelope. Their size ranges from tens to a few hundred nanometers, and their numbers increase as plastids differentiate from chloroplasts to chromoplasts or during stress and aging.

Biochemically, plastoglobuli consist mainly of neutral lipids such as triacylglycerols and other esterified lipids, along with pigments and isoprenoids including carotenoids, tocopherols, and plastoquinone. A set of abundant proteins, collectively known as plastoglobulins (the FBN family), is also a major constituent, and various enzymes involved in lipid metabolism can be associated with these particles.

Functionally, plastoglobuli serve as lipid storage and as sites for lipid remodeling and isoprenoid metabolism within plastids. During stress or senescence, lipids and antioxidants are mobilized between thylakoid membranes and plastoglobuli, and plastoglobuli may participate in the turnover of prenyl lipids and in protecting the photosynthetic apparatus from oxidative damage. They are thought to help stabilize thylakoid membranes as the internal composition of the plastid changes.

Occurrence and dynamics, Plastoglobuli proliferate and enlarge during leaf senescence, etiolation in darkness, drought, high light, and chromoplast differentiation. Their abundance correlates with plastid developmental state and they are often used as indicators of lipid remodeling within plastids.

Significance, Plastoglobuli are widely present in plant plastids and algae, making them a focus of study for understanding lipid metabolism, plastid development, and plant responses to environmental stress.