Intersection of the tocopherol and plastoquinol metabolic pathways at the plastoglobule

Anna Maria Zbierzak , Marion Kanwischer , Christina Wille , Pierre-Alexandre Vidi , Patrick Giavalisco , Antje Lohmann , Isabel Briesen , Svetlana Porfirova , Claire Bréhélin , Felix Kessler , Peter Dörmann (1)

1 Institute of Molecular Physiology and Biotechnology of Plants

Plastoglobules, lipid-protein bodies in the stroma of plant chloroplasts, are enriched in non-polar lipids, in particular prenyl quinols. Here we show that in addition to the thylakoids, plastoglobules also contain a considerable proportion of the plastidial plastoquinol-9 (PQ-9), the redox component of photosystem II, and of the cyclized product of PQ-9, plastochromanol-8 (PC-8), a tocochromanol with a structure similar to γ-tocopherol and γ-tocotrienol, but with a C40 prenyl side chain. PC-8 formation was abolished in the Arabidopsis thaliana tocopherol cyclase mutant vte1, but accumulated in VTE1 overexpression plants, in agreement with a role of tocopherol cyclase (VTE1) in PC-8 synthesis. VTE1 overexpression resulted in the proliferation of the number of plastoglobules which occurred in the form of clusters in the transgenic lines. Simultaneous overexpression of VTE1 and of the methyltransferase VTE4 resulted in the accumulation of a compound tentatively identified as 5-methyl-PC-8, the methylated form of PC-8. Our data suggest that the existence of a plastoglobular pool of PQ-9, along with the partial conversion of PQ-9 into PC-8, might represent a mechanism for the regulation of the antioxidant content in thylakoids and of the PQ-9 pool that is available for photosynthesis.

Mots clés: Life Sciences

Anna Maria Zbierzak, Marion Kanwischer, Christina Wille, Pierre-Alexandre Vidi, Patrick Giavalisco, et al.. Intersection of the tocopherol and plastoquinol metabolic pathways at the plastoglobule. Biochemical Journal, 2009, 425 (2), pp.389-399. ⟨10.1042/BJ20090704⟩. ⟨hal-00479193⟩