Characterization of an Arabidopsis mutant deficient in γ-tocopherol methyltransferase

被引:119
作者
Bergmüller, E [1 ]
Porfirova, S [1 ]
Dörmann, P [1 ]
机构
[1] Max Planck Inst Mol Plant Physiol, Dept Lothar Willmitzer, D-14476 Golm, Germany
关键词
lipid; mutant; oxidative stress; tocopherol; vitamin E;
D O I
10.1023/B:PLAN.0000004307.62398.91
中图分类号
Q5 [生物化学]; Q7 [分子生物学];
学科分类号
071010 ; 081704 ;
摘要
Alpha-tocopherol (vitamin E) is synthesized from gamma-tocopherol in chloroplasts by gamma-tocopherol methyltransferase (gamma-TMT; VTE4). Leaves of many plant species including Arabidopsis contain high levels of alpha-tocopherol, but are low in gamma-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 gamma-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 gamma-TMT was identified in a T-DNA tagged mutant population. In vte4-1 and vte4-2 leaves, high levels of gamma-tocopherol accumulated, whereas alpha-tocopherol was absent indicating that, presumably, these two mutants represents null alleles. Over-expression of the gamma-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 alpha-tocopherol and gamma-tocopherol increased in wild type, and gamma-tocopherol in vte4-1. However, chlorophyll content and photosynthetic quantum yield were very similar in wild type and vte4-1, suggesting that alpha-tocopherol can be replaced by gamma-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.
引用
收藏
页码:1181 / 1190
页数:10
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