Intersection of the tocopherol and plastoquinol metabolic pathways at the plastoglobule.
Plastoglobules, lipid-protein bodies in the stroma of plant chloroplasts, are enriched in non-polar lipids, in particular prenyl quinols. In the present study we show that, in addition to the thylakoids, plastoglobules also contain a considerable proportion of the plastidial PQ-9 (plastoquinol-9), the redox component of photosystem II, and of the cyclized product of PQ-9, PC-8 (plastochromanol-8), a tocochromanol with a structure similar to gamma-tocopherol and gamma-tocotrienol, but with a C-40 prenyl side chain. PC-8 formation was abolished in the Arabidopsis thaliana tocopherol cyclase mutant vte1, but accumulated in VTE1-overexpressing 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. The results of the present study 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.
Institute of Molecular Physiology and Biotechnology of Plants, University of Bonn, Karlrobert-Kreiten-Strasse 13, 531115 Bonn, Germany.
Anna Maria
AM
Zbierzak
Marion
M
Kanwischer
Christina
C
Wille
Pierre-Alexandre
PA
Vidi
Patrick
P
Giavalisco
Antje
A
Lohmann
Isabel
I
Briesen
Svetlana
S
Porfirova
Claire
C
Bréhélin
Felix
F
Kessler
Peter
P
Dörmann
D000975:Antioxidants; D017360:Arabidopsis / Q000378:metabolism*; D029681:Arabidopsis Proteins / Q000378:metabolism; D002736:Chloroplasts / Q000378:metabolism* / Q000648:ultrastructure; D002839:Chromans; D019751:Intramolecular Transferases / Q000378:metabolism; D053858:Metabolic Networks and Pathways; D010788:Photosynthesis; D010971:Plastoquinone / Q000031:analogs & derivatives* / Q000378:metabolism; D020524:Thylakoids; D024505:Tocopherols / Q000378:metabolism*; D014810:Vitamin E / Q000031:analogs & derivatives / Q000096:biosynthesis
D000975:Antioxidants; D029681:Arabidopsis Proteins; D002839:Chromans; D014810:Vitamin E; C003165:plastoquinol; C013649:plastochromanol 8; D019751:Intramolecular Transferases; C103397:tocopherol cyclase; D010971:Plastoquinone; D024505:Tocopherols