Genetic evidence for the role of GDP-mannose in plant ascorbic acid (vitamin C) biosynthesis
Genetic evidence for the role of GDP-mannose in plant ascorbic acid (vitamin C) biosynthesis
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DOI：
10.1073/pnas.96.7.4198
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发表时间：
1999-03-30
影响因子：
11.1
通讯作者：
Last, RL
中科院分区：
文献类型：
--
作者：
Conklin, PL;Norris, SR;Last, RL
维生素C（L-抗坏血酸;阿萨）在植物和动物中作为一种有效的抗氧化剂和细胞还原剂。阿萨在植物中具有重要的生理作用，但其生物合成机制目前还没有明确。最近提出了一种植物阿萨生物合成途径，其特征在于GDP-甘露糖和L-半乳糖。我们已经分离出一系列拟南芥AsA缺陷突变体，这些突变体是测试阿萨生物合成途径的有价值的工具。这些突变体（vtc 1）的最佳特征包含约25%的野生型阿萨，并在阿萨生物合成缺陷。通过使用生物化学，分子和遗传技术的组合，我们已经证明，VTC 1基因座编码GDP-甘露糖焦磷酸化酶（甘露糖-1-P鸟苷转移酶）。该酶提供GDP-甘露糖，其用于细胞壁碳水化合物生物合成和蛋白质糖基化以及Ash生物合成。除了从遗传学上定义参与阿萨生物合成的第一个位点外，这项工作还强调了使用传统诱变技术结合拟南芥基因组计划快速克隆生理学上重要基因的能力。
Vitamin C (L-ascorbic acid; AsA) acts as a potent antioxidant and cellular reductant in plants and animals. AsA has long been known to have many critical physiological roles in plants, yet its biosynthesis is only currently being defined. A pathway for AsA biosynthesis that features GDP-mannose and L-galactose has recently been proposed for plants. We have isolated a collection of AsA-deficient mutants of Arabidopsis thaliana that are valuable tools for testing of an AsA biosynthetic pathway. The best-characterized of these mutants (vtc1) contains approximate to 25% of wildtype AsA and is defective in AsA biosynthesis. By using a combination of biochemical, molecular, and genetic techniques, we have demonstrated that the VTC1 locus encodes a GDP-mannose pyrophosphorylase (mannose-1-P guanyltransferase). This enzyme provides GDP-mannose, which is used for cell wall carbohydrate biosynthesis and protein glycosylation as well as for Ash biosynthesis. In addition to genetically defining the first locus involved in AsA biosynthesis, this work highlights the power of using traditional mutagenesis techniques coupled with the Arabidopsis Genome Initiative to rapidly clone physiologically important genes.