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          Institute: MPI für molekulare Pflanzenphysiologie     Collection: Publikationen Pflanzenphysiologie     Display Documents



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ID: 248406.0, MPI für molekulare Pflanzenphysiologie / Publikationen Pflanzenphysiologie
Alterations in tocopherol cyclase activity in transgenic and mutant plants of arabidopsis affect tocopherol content, tocopherol composition, and oxidative stress
Authors:Kanwischer, M.; Porfirova, S.; Bergmuller, E.; Dormann, P.
Language:English
Date of Publication (YYYY-MM-DD):2005-02
Title of Journal:Plant Physiology
Journal Abbrev.:Plant Physiol
Volume:137
Issue / Number:2
Start Page:713
End Page:723
Review Status:not specified
Audience:Not Specified
Abstract / Description:Tocopherol belongs to the Vitamin E class of lipid soluble antioxidants that are essential for human nutrition. In plants, tocopherol is synthesized in plastids where it protects membranes from oxidative degradation by reactive oxygen species. Tocopherol cyclase (VTE1) catalyzes the penultimate step of tocopherol synthesis, and an Arabidopsis (Arabidopsis thaliana) mutant deficient in VTE1 (vte1) is totally devoid of tocopherol. Overexpression of VTE1 resulted in an increase in total tocopherol of at least 7-fold in leaves, and a dramatic shift from a-tocopherol to gamma-tocopherol. Expression studies demonstrated that indeed VTE1 is a major limiting factor of tocopherol synthesis in leaves. Tocopherol deficiency in vte1 resulted in the increase in ascorbate and glutathione, whereas accumulation of tocopherol in VTE1 overexpressing plants led to a decrease in ascorbate and glutathione. Deficiency in one antioxidant in vte1, vtc1 (ascorbate deficient), or cad2 (glutathione deficient) led to increased oxidative stress and to the concomitant increase in alternative antioxidants. Double mutants of vte1 were generated with vtc1 and cad2. Whereas growth, chlorophyll content, and photosynthetic quantum yield were very similar to wild type in vte1, vtc1, cad2, or vte1vtc1, they were reduced in vte1cad2, indicating that the simultaneous loss of tocopherol and glutathione results in moderate oxidative stress that affects the stability and the efficiency of the photosynthetic apparatus.
Free Keywords:synechocystis sp pcc-6803
; vitamin-e content
; homogentisate phytyltransferase
; ascorbic-acid
; lipid-peroxidation
; chlorophyll fluorescence
; glutathione-deficient
; spinach-chloroplasts
; biosynthesis
; thaliana
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für molekulare Pflanzenphysiologie/Molekulare Physiologie/AG Doermann
External Affiliations:Max Planck Inst Mol Plant Physiol, Dept Lothar Willmitzer, D-14476 Golm, Germany
Max Planck Inst Mol Plant Physiol, Dept Lothar Willmitzer, D-14476 Golm, Germany
Identifiers:ISI:000227116900027 [ID No:1]
ISI:000227116900027 [ID No:2]
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