Building the Synthetic Biology Toolbox with Enzyme Variants to Expand Opportunities for Biofortification of Provitamin A and Other Health-Promoting Carotenoids.
Building the Synthetic Biology Toolbox with Enzyme Variants to Expand Opportunities for Biofortification of Provitamin A and Other Health-Promoting Carotenoids.
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DOI：
10.1021/acs.jafc.0c04740
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发表时间：
2020-10
影响因子：
6.1
通讯作者：
Kaijie Zhu;Xiongjie Zheng;Junli Ye;Q. Jiang;Hongyan Chen;Xuehan Mei;E. Wurtzel;X. Deng
中科院分区：
文献类型：
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作者：
Kaijie Zhu;Xiongjie Zheng;Junli Ye;Q. Jiang;Hongyan Chen;Xuehan Mei;E. Wurtzel;X. Deng
类胡萝卜素是一大类对人体健康很重要的结构，包括维生素原a和非维生素原a化合物。维生素A缺乏症是一个全球性的健康问题，可以通过在一系列粮食作物中丰富维生素A原类胡萝卜素来缓解。适合生物强化的植物是那些维生素A原生物合成前体番茄红素含量高的植物，番茄红素可以通过番茄红素β-环化酶（LCYB）转化为维生素A原类胡萝卜素β-胡萝卜素。农作物，如柑橘，自然积累高水平的维生素原A和其他促进健康的类胡萝卜素。这类植物可能拥有有用的基因，以扩大合成生物学工具箱，以生产一系列表型，包括高维生素a原作物和具有独特的促进健康的类胡萝卜素成分的作物。为了研究具有不同活性水平的酶变体，我们将两个柑橘LCYB等位基因引入到富含番茄红素的番茄中。在番茄中过度表达柑橘色质体特异性番茄红素β-环化酶（CsLCYb2a）的强等位基因产生了“金色”转基因番茄果实，当干重达到1.5 mg/g时，其β-胡萝卜素含量增加了9.3倍。使用较弱的等位基因CsLCYb2b也导致β-胡萝卜素水平的提高，但在类胡萝卜素组成更为异质性的背景下。从合成生物学的角度来看，这些等位基因的差异对生产具有独特类胡萝卜素特征的品种具有价值。柑橘LCYB基因的过表达伴随着编码类胡萝卜素生物合成酶的其他基因的表达增加，以及在转基因番茄果实中吸收高水平的类胡萝卜素所需的色质体的大小和数量增加。柑橘LCYB基因的过度表达也导致了植物激素和初级代谢产物谱的多效性影响。我们的研究结果表明，酶变体是创造更广泛的代谢工程产品所必需的合成生物学部分。在这种情况下，LCYB的强变体和弱变体被证明在创造饮食来源以减轻维生素A缺乏症方面是有用的，或者，创造含有多种成分的作物，包括维生素A原和健康的非维生素A原类胡萝卜素。
Carotenoids are a large class of structures that are important in human health and include both provitamin A and nonprovitamin A compounds. Vitamin A deficiency is a global health problem that can be alleviated by enriching provitamin A carotenoids in a range of food crops. Suitable plants for biofortification are those with high levels of the provitamin A biosynthetic precursor, lycopene, which is enzymatically converted by lycopene β-cyclase (LCYB) to β-carotene, a provitamin A carotenoid. Crops, such as citrus, naturally accumulate high levels of provitamin A and other health-promoting carotenoids. Such plants may have useful genes to expand the synthetic biology toolbox for producing a range of phenotypes, including both high provitamin A crops and crops with unique compositions of health-promoting carotenoids. To examine enzyme variants having different activity levels, we introduced two citrus LCYB alleles into tomato, a plant with fruit rich in lycopene. Overexpression in tomato of the stronger allele of the citrus chromoplast-specific lycopene β-cyclase (CsLCYb2a) produced "golden" transgenic tomato fruits with 9.3-fold increased levels of β-carotene at up to 1.5 mg/g dry weight. The use of the weaker allele, CsLCYb2b, also led to enhanced levels of β-carotene but in the context of a more heterogeneous composition of carotenoids. From a synthetic biology standpoint, these allelic differences have value for producing cultivars with unique carotenoid profiles. Overexpression of the citrus LCYB genes was accompanied by increased expression of other genes encoding carotenoid biosynthetic enzymes and increased size and number of chromoplasts needed to sequester the elevated levels of carotenoids in the transgenic tomato fruits. The overexpression of the citrus LCYB genes also led to a pleiotropic effect on profiles of phytohormones and primary metabolites. Our findings show that enzyme variants are essential synthetic biology parts needed to create a wider range of metabolic engineering products. In this case, strong and weak variants of LCYB proved useful in creating dietary sources to alleviate vitamin A deficiency or, alternatively, to create crops with a heterogeneous composition including provitamin A and healthful, nonprovitamin A carotenoids.