New functions of plastoglobules in Vitamin E and K metabolism
Project responsable Félix Kessler
Team member Celine Besagni
Abstract Vitamins E and K are important components of nutrition and essential for human health. Vitamin E (tocopherol group) consists of closely related lipid-soluble antioxidants. They inhibit reactive oxygen species production due to lipid peroxidation. Vitamin K (phyllo-/menaquinone group) are lipid-soluble compounds that are necessary for modification of proteins implicated in blood coagulation. Together with plastoquinone, Vitamins E and K belong to the family of prenylquinone compounds. In plants, these are synthesized mostly in the chloroplast and carry important roles as lipid antioxidants (tocopherol) and/or electron carriers in photosynthesis (phylloquinone and plastoquinone), respectively. The photosynthetic light reactions in the chloroplast take place at the thylakoid membrane and this is where the prenylquinones fulfill most of their essential roles in plants. In contrast, most of the biosynthetic reactions take place in the envelope membranes. But we recently discovered that chloroplast lipid droplets called plastglobules that tightly associate with the thylakoid membrane also play an essential role in prenylquinone metabolism. Using a proteomics approach we identified about 30 different proteins coating plastoglobules. These ranged from the structural plastoglobulins, to a number of known enzymes (including the tocopherol cyclase VTE1 required for tocopherol biosynthesis) as well as uncharacterized proteins mostly predicted to be involved in lipid metabolism. We therefore tested the hypothesis that plastoglobules are indeed implicated in lipid and more specifically in prenylquinone metabolism. Using state of the art lipidomics techniques, among others, this lead to the discovery of essential metabolic roles of plastoglobules in Vitamin E (tocopherol) and Vitamin K (phylloquinone) accumulation. More important functions certainly remain to be discovered. This project has three aims and implicates a broad range of techniques: A) to systematically unravel the function of several yet uncharacterized plastoglobule proteins. These have hypothetical functions in the regulation of prenylquinone synthesis and their trafficking between plastoglobules and the thylakoid membrane. B) to adress the hypothesis that plastoglobules are implicated in the biogenesis of the thylakoid membrane early in seedling development. C) to discover new genes that are required for correct plastoglobule function and function.
Keywords metabolism, Lipids droplets, chloroplast, vitamin E, Vitamin K, lipidomic, plastoglobules
Type of project Fundamental research project
Research area Biologie cellulaire, cytologie
Method of financing FNS - Encouragement de projets (Div. I-III)
Status Completed
Start of project 1-8-2012
End of project 31-7-2015
Overall budget 244'027.00
Additional info http://p3.snf.ch/projects-141229#
Contact Félix Kessler