Recent advances in carotenoid biosynthesis, regulation and manipulation
Recent advances in carotenoid biosynthesis, regulation and manipulation
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DOI：
10.1007/s00425-005-1533-5
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发表时间：
2005-06-01
期刊：
影响因子：
4.3
通讯作者：
Fraser, PD
中科院分区：
文献类型：
--
作者：
Römer, S;Fraser, PD
类胡萝卜素是自然界中发现的最广泛的一组色素。在植物中，类胡萝卜素在发育、光合作用和膜稳定性中具有功能性作用。它们充当植物激素前体（Schwartz等人，2003年），并参与环境适应（Demmig-亚当斯和亚当斯，2002年）。类胡萝卜素由于其高抗氧化潜力而发挥保护功能，并且也是人类饮食的重要组成部分。强有力的证据表明，富含类胡萝卜素的饮食可以预防某些慢性疾病（Mares-Perlman et al. 2002）和某些癌症（Giovannucci 2002）的发生。类胡萝卜素生物合成途径的阐明和基因克隆的巨大进展提供了进行该途径的代谢工程（也称为遗传操作或工程）所必需的工具（最近的综述，参见Tucker 2003; Fraser and Bramley 2004）。这导致稳定的转基因植物具有改善的营养品质、增加的合成高价值类胡萝卜素的能力和增强的对非生物胁迫的耐受性。大多数操作都针对途径中的单个步骤，目的是提高番茄红素和b-胡萝卜素含量。几种组成型过表达方法（Fray等，1995; Busch等，2002）集中于八氢番茄红素合酶（PSY），并导致各种非预期的多效性和/或共抑制效应。这些实验还揭示了不同类异戊二烯形成途径之间微妙的前体平衡和复杂的相互作用（比较Laule等人，2003）。在大多数情况下，使用显示高器官或发育特异性的启动子与低同源性转基因的组合成功地提高了类胡萝卜素含量，避免了共抑制效应并减少了转化植物中的代谢扰动（Fraser等，2002; Shewmaker等，1999）。由于其维生素A原活性，增加作物和蔬菜中的b-胡萝卜素水平也一直是基因工程的主要目标。不同番茄红素环化酶的过表达产生了具有显著更高的b-胡萝卜素含量的番茄果实（综述于Fraser和Bramley 2004）。在油菜籽中，Ravanello et al.（2003）已经产生了含有编码来自细菌来源的PSY和八氢番茄红素去饱和酶以及植物或细菌来源的番茄红素环化酶的基因的三重构建体。不幸的是，这些构建体对先前仅用细菌PSY获得的构建体几乎没有改进。所谓的“黄金大米”的生产是指在通常缺乏类胡萝卜素的水稻胚乳中合成b-胡萝卜素（维生素A原）的工程，也需要从不同来源转移几个基因以获得所需的特性（Ye等人，2000年）。为了提供维生素原A含量高的主食来源，从而缓解发展中国家的维生素A缺乏症，最近将维生素原A表型转移到两个在目标国家广泛种植的籼稻品种中（Hoa等人，2003年）迈出了第一步商业开发。作者还修改了他们的结构，
Carotenoids are the most widespread group of pigments found in nature. In plants, carotenoids have functional roles in development, photosynthesis and membrane stability. They act as phytohormone precursors (Schwartz et al. 2003) and are involved in environmental adaptation (Demmig-Adams and Adams 2002). Carotenoids exert protective functions due to their high antioxidative potential and are also important components of the human diet. Strong evidence suggests that diets rich in carotenoids can prevent the onset of some chronic disease states (Mares-Perlman et al. 2002) and certain cancers (Giovannucci 2002). The elucidation of the carotenoid biosynthetic pathway and the enormous progress in gene cloning provided the tools necessary to embark upon the metabolic engineering (also termed genetic manipulation or engineering) of the pathway (for recent reviews, see Tucker 2003; Fraser and Bramley 2004). This has resulted in stable transgenic plants with improved nutritional quality, increased ability to synthesise high value carotenoids and enhanced tolerance to abiotic stress. The majority of manipulations have targeted single steps in the pathway with the objective to elevate the lycopene and b-carotene content. Several constitutive overexpression approaches (Fray et al. 1995; Busch et al. 2002) focused on phytoene synthase (PSY), and led to various unintended pleiotropic and/or co-suppression effects. These experiments also revealed the delicate precursor balance and intricate interaction between different isoprenoid forming pathways (compare Laule et al. 2003). The use of promoters showing high organ or developmental specificity in combination with low homology transgenes successfully elevated the carotenoid content, avoided co-suppression effects and reduced metabolic perturbances in the transformed plants (Fraser et al. 2002; Shewmaker et al. 1999) in most cases. Due to its pro-vitamin A activity, increasing b-carotene level in crops and vegetables has also been a primary goal of genetic engineering. Over-expression of different lycopene cyclases gave rise to tomato fruits with significantly higher b-carotene content (reviewed in Fraser and Bramley 2004).Recently, multiple carotenoid genes were transformed into plants in an attempt to further increase the amount of total carotenoids. In canola seeds, Ravanello et al.(2003) have generated a triple construct containing genes encoding PSY and phytoene desaturase from a bacterial source as well as lycopene cyclases of either plant or bacterial origin. Unfortunately, these constructs have made little improvement to that obtained previously with a bacterial PSY solely. The production of the so-called ‘‘golden rice’’referring to the engineering of b-carotene (pro-vitamin A) synthesis in normally carotenoid-devoid rice endosperm also required the transfer of several genes from different origins to obtain the desired property (Ye et al. 2000). To provide a staple food source high in provitamin A thereby alleviating vitamin A deficiency in developing countries, the provitamin A phenotype was recently transferred into two Indica rice varieties which are widely grown in the target countries (Hoa et al. 2003) taking first steps to commercial exploitation. The authors also modified their construct by replacing the controversially discussed