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Eugeni Piller, Lucia
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Eugeni Piller, Lucia
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3 Résultats
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- PublicationAccès libreRole of plastoglobules in metabolite repair in the tocopherol redox cycle
; ; Besagni, CélinePlants are exposed to ever changing light environments and continuously forced to adapt. Excessive light intensity leads to the production of reactive oxygen species that can have deleterious effects on photosystems and thylakoid membranes. To limit damage, plants increase the production of membrane soluble antioxidants such as tocopherols. Here, untargeted lipidomics after high light treatment showed that among hundreds of lipid compounds alpha-tocopherol is the most strongly induced, underscoring its importance as an antioxidant. As part of the antioxidant mechanism, a-tocopherol undergoes a redox cycle involving oxidative opening of the chromanol ring. The only enzyme currently known to participate in the cycle is tocopherol cyclase (VTE1, At4g32770), that re-introduces the chromanol ring of a-tocopherol. By mutant analysis, we identified the NAD(P)H-dependent quinone oxidoreductase (NDC1, At5g08740) as a second enzyme implicated in this cycle. NDC1 presumably acts through the reduction of quinone intermediates preceding cyclization by VTE1. Exposure to high light also triggered far-ranging changes in prenylquinone composition that we dissect herein using null mutants and lines overexpressing the VTE1 and NDC1 enzymes. - PublicationAccès librePlastid lipid droplets at the crossroads of prenylquinone metabolism
; ; Besagni, CélineLipid droplets called plastoglobules (PGs) exist in most plant tissues and plastid types. In chloroplasts, the polar lipid monolayer surrounding these low-density lipoprotein particles is continuous with the outer lipid leaflet of the thylakoid membrane. Often small clusters of two or three PGs, only one of them directly connected to thylakoids, are present. Structural proteins (known as plastid-lipid associated proteins/fibrillins or plastoglobulins) together with lipid metabolic enzymes coat the PGs. The hydrophobic core of PGs contains a range of neutral lipids including the prenylquinones [tocopherols (vitamin E), phylloquinone (vitamin K1), and plastoquinone (PQ-9)]. In this review the function of PGs and their associated enzymes in prenylquinone metabolism will be discussed. - PublicationAccès libreChloroplast lipid droplet type II NAD(P)H quinone oxidoreductase is essential for prenylquinone metabolism and vitamin K(1) accumulation
; ; Havaux, MichelLipid droplets are ubiquitous cellular structures in eukaryotes and are required for lipid metabolism. Little is currently known about plant lipid droplets other than oil bodies. Here, we define dual roles for chloroplast lipid droplets (plastoglobules) in energy and prenylquinone metabolism. The prenylquinones—plastoquinone, plastochromanol-8, phylloquinone (vitamin K(1)), and tocopherol (vitamin E)—are partly stored in plastoglobules. This work shows that NAD(P)H dehydrogenase C1 (NDC1) (At5g08740), a type II NAD(P)H quinone oxidoreductase, associates with plastoglobules. NDC1 reduces a plastoquinone analog in vitro and affects the overall redox state of the total plastoquinone pool in vivo by reducing the plastoquinone reservoir of plastoglobules. Finally, NDC1 is required for normal plastochromanol-8 accumulation and is essential for vitamin K(1) production.