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Plastoglobules

Chloroplast and plastid lipo-protein micro-compartments, named plastoglobules (PG). Chloroplasts in leaves but also chromoplasts in fruits and flowers, and other plastid types in non-photosynthetic tissues, contain dynamic lipid-protein monolayer particles (PG).  These particles are filled with vitamin E (tocopherol), and various other isoprenoids such as plastochromanol-8 and plastoquinone, as well as vitamin K1. These PGs function in the metabolism of these isoprenoids but are also important for recycling of the lipids and pigments (e.g. chlorophyll and carotenoids) in thylakoid membranes during abiotic stresses and during senescence. Using mass spectrometry, we identified more than 30 proteins in these PG; some have known functions such as tocopherol cyclase (VTE1) involved in vitamin E biosynthesis, whereas the functions of most others are unknown. The van Wijk lab studies how PG and its proteins contribute to plant metabolism, leaf development and aging as well as abiotic stress defense. For instance, we observed that null mutants for several PG localized ABC1 kinases are light sensitive and also cannot cope well with nitrogen starvation. Understanding the function of these PG is essential for understanding chloroplast metabolism and stress responses, ultimately providing opportunities for more stress resistant plants and increased agricultural production. For an overview of PG functions,  read  van Wijk and Kessler (2017).

PG have different functionalities in different plastid types (Figures from van Wijk and Kessler 2017 Annual Review Plant Biology)

 

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