Chloroplasts contain lipoprotein particles termed plastoglobules. Plastoglobules are
generally believed to have little function beyond lipid storage. Here we report on
the identification of plastoglobule proteins using mass spectrometry methods in Arabidopsis
thaliana. We demonstrate specific plastoglobule association of members of the plastid
lipid-associated proteins/fibrillin family as well as known metabolic enzymes, including
the tocopherol cyclase (VTE1), a key enzyme of tocopherol ( vitamin E) synthesis.
Moreover, comparative analysis of chloroplast membrane fractions shows that plastoglobules
are a site of vitamin E accumulation in chloroplasts. Thus, in addition to their lipid
storage function, we propose that plastoglobules are metabolically active, taking
part in tocopherol synthesis and likely other pathways.
