Genetic dissection of carotenoid synthesis in arabidopsis defines plastoquinone as an essential component of phytoene desaturation
Genetic dissection of carotenoid synthesis in arabidopsis defines plastoquinone as an essential component of phytoene desaturation
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DOI：
10.1105/tpc.7.12.2139
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发表时间：
1995-12-01
期刊：
影响因子：
11.6
通讯作者：
DellaPenna, D
中科院分区：
文献类型：
--
作者：
Norris, SR;Barrette, TR;DellaPenna, D
类胡萝卜素是由位于高等植物质体中的核编码多酶复合物合成的 C-40 四萜类化合物。为了进一步了解类胡萝卜素合成中涉及的成分和机制，我们筛选了拟南芥中是否存在破坏该途径并导致生物合成中间体积累的突变。在这里，我们报告了两个非等位基因白化突变 pds1 和 pds2（用于八氢番茄红素去饱和）的鉴定和表征，它们在八氢番茄红素去饱和过程中被破坏，并因此积累了八氢番茄红素（该途径的第一个 C-40 化合物）。令人惊讶的是，这两种突变都没有映射到编码八氢番茄红素去饱和酶的基因座，这表明至少需要三个基因座的产物 高等植物中的八氢番茄红素去饱和，因为八氢番茄红素去饱和酶催化氧化反应，因此有人认为电子传递链的成分可能参与该反应，pds1和pds2的分析表明，这两个突变体除了无法使八氢番茄红素去饱和之外，还缺乏质体醌和生育酚，质体醌/生育酚生物合成的单独步骤 pds1 突变影响 4-羟苯基丙酮酸双加氧酶，因为它可以通过在产物上生长而被拯救，但不能通过该酶的底物尿黑酸和 4-羟苯基丙酮酸分别生长。 pds2 突变最有可能影响该酶的苯基/植基转移酶 由于绿藻斜生栅藻中缺乏生育酚的突变体可以合成类胡萝卜素，我们的研究结果最终证明质体醌是类胡萝卜素合成的重要成分。我们提出了光合组织中类胡萝卜素合成的模型，其中质体醌充当类胡萝卜素去饱和酶和光合电子传递链之间的中间电子载体。
Carotenoids are C-40 tetraterpenoids synthesized by nuclear-encoded multienzyme complexes located in the plastids of higher plants. To understand further the components and mechanisms involved in carotenoid synthesis, we screened Arabidopsis for mutations that disrupt this pathway and cause accumulation of biosynthetic intermediates. Here, we report the identification and characterization of two nonallelic albino mutations, pds1 and pds2 (for phytoene desaturation), that are disrupted in phytoene desaturation and as a result accumulate phytoene, the first C-40 compound of the pathway, Surprisingly, neither mutation maps to the locus encoding the phytoene desaturase enzyme, indicating that the products of at least three loci are required for phytoene desaturation in higher plants, Because phytoene desaturase catalyzes an oxidation reaction, it has been suggested that components of an electron transport chain may be involved in this reaction, Analysis of pds1 and pds2 shows that both mutants are plastoquinone and tocopherol deficient, in addition to their inability to desaturate phytoene, Separate steps of the plastoquinone/tocopherol biosynthetic pathway are affected by these two mutations, The pds1 mutation affects the enzyme 4-hydroxyphenylpyruvate dioxygenase because it can be rescued by growth on the product but not the substrate of this enzyme, homogentisic acid and 4-hydroxyphenylpyruvate, respectively The pds2 mutation most likely affects the phenyl/phytyl transferase enzyme of this pathway, Because tocopherol-deficient mutants in the green alga Scenedesmus obliquus can synthesize carotenoids, our findings demonstrate conclusively that plastoquinone is an essential component in carotenoid synthesis. We propose a model for carotenoid synthesis in photosynthetic tissue whereby plastoquinone acts as an intermediate electron carrier between carotenoid desaturases and the photosynthetic electron transport chain.