plastoglobulin

Plastoglobulin is a term used for a family of small, lipid-associated proteins that localize to plastoglobules in chloroplasts and chromoplasts. Plastoglobules are discrete, lipid-rich particles within plastids that increase in number and size during senescence and stress, serving as reservoirs for lipids and redox-active prenylquinones.

Most plastoglobulins are encoded by nuclear genes and contain a transit peptide for import into plastids. In mature plastids they associate with the surface of plastoglobules and often exist as homo- or heterooligomers with fibrillin proteins (FBNs), contributing to the organization of the plastoglobule matrix.

Functional data indicate roles in lipid metabolism and storage, including turnover of tocopherols (vitamin E), plastoquinone, and other isoprenoids. They may participate in remodeling of thylakoid membranes during light acclimation and senescence, and in the plant stress response. Some plastoglobulins show transcriptional upregulation under oxidative stress or aging, and loss-of-function mutants can exhibit altered plastoglobule size, composition, or plastid lipid metabolism, though there is substantial functional divergence among family members.

Several plastoglobulins have been characterized in model species such as Arabidopsis thaliana, with specific members designated PGL1, PGL2, PGL3, etc., and there is overlap with the fibrillin (FBN) family of plastid-associated proteins. The exact molecular activities of many plastoglobulins remain an active area of research.