Characterization of an Arabidopsis mutant deficient in γ-tocopherol methyltransferase

Characterization of an Arabidopsis mutant deficient in γ-tocopherol methyltransferase Alpha-tocopherol (vitamin E) is synthesized from γ-tocopherol in chloroplasts by γ-tocopherol methyltransferase (γ-TMT; VTE4). Leaves of many plant species including Arabidopsis contain high levels of α-tocopherol, but are low in γ-tocopherol. To unravel the function of different forms of tocopherol in plants, an Arabidopsis plant (vte4-1) carrying a functional null mutation in the gene γ-TMT was isolated by screening a mutant population via thin-layer chromatography. A second mutant allel (vte4-2) carrying a T-DNA insertion in the coding sequence of γ-TMT was identified in a T-DNA tagged mutant population. In vte4-1 and vte4-2 leaves, high levels of γ-tocopherol accumulated, whereas α-tocopherol was absent indicating that, presumably, these two mutants represents null alleles. Over-expression of the γ-TMT cDNA in vte4-1 restored wild-type tocopherol composition. Mutant plants were very similar to wild type. During oxidative stress (high light, high temperature, cold treatment) the amounts of α-tocopherol and γ-tocopherol increased in wild type, and γ-tocopherol in vte4-1. However, chlorophyll content and photosynthetic quantum yield were very similar in wild type and vte4-1, suggesting that α-tocopherol can be replaced by γ-tocopherol in vte4-1 to protect the photosynthetic apparatus against oxidative stress. Fatty acid and lipid composition were very similar in WT, vte4-1 and vte1, an Arabidopsis mutant previously isolated which is completely devoid of tocopherol. Therefore, a shift in tocopherol composition or the absence of tocopherol has no major impact on the amounts of specific fatty acids or on lipid hydrolysis. Plant Molecular Biology Springer Journals

Characterization of an Arabidopsis mutant deficient in γ-tocopherol methyltransferase

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Kluwer Academic Publishers
Copyright © 2003 by Kluwer Academic Publishers
Life Sciences; Biochemistry, general; Plant Sciences; Plant Pathology
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