Kim Hyojin, Liu Lingyi, Han Lihua, Park Kiyoul, Kim Hae Jin, Nguyen Tam, Nazarenus Tara J, Cahoon Rebecca E, Haslam Richard P, Ciftci Ozan, Napier Johnathan A, Cahoon Edgar B
Center for Plant Science Innovation and Department of Biochemistry, University of Nebraska-Lincoln, Lincoln, NE, USA.
Department of Food Science and Technology, University of Nebraska-Lincoln, Lincoln, NE, USA.
Plant Biotechnol J. 2025 Aug;23(8):3451-3464. doi: 10.1111/pbi.70148. Epub 2025 Jun 3.
Ketocarotenoids, including astaxanthin, are red lipophilic pigments derived from the oxygenation of β-carotene ionone rings. These carotenoids have exceptional antioxidant capacity and high commercial value as natural pigments, especially for aquaculture feedstocks to confer red flesh colour to salmon and shrimp. Ketocarotenoid biosynthetic pathways occur only in selected bacterial, algal, fungal and plant species, which provide genetic resources for biotechnological ketocarotenoid production. Toward pathway optimization, we developed a transient platform for ketocarotenoid production using Agrobacterium infiltration of Nicotiana benthamiana leaves with plant (Adonis aestivalis) genes, carotenoid β-ring 4-dehydrogenase 2 (CBFD2) and carotenoid 4-hydroxy-β-ring 4-dehydrogenase (HBFD1), or bacterial (Brevundimonas) genes, β-carotene ketolase (crtW) and β-carotene hydroxylase (crtZ). In this test system, heterologous expression of the plant-derived astaxanthin pathway conferred higher astaxanthin production with fewer ketocarotenoid intermediates than the bacterial pathway. We evaluated the plant-derived pathway for ketocarotenoid production using the oilseed camelina (Camelina sativa) as a production platform. Genes for CBFD2 and HBFD1 and maize phytoene synthase were introduced under the control of seed-specific promoters. In contrast to prior research with bacterial pathways, our strategy resulted in nearly complete conversion of β-carotene to ketocarotenoids, including primarily astaxanthin. Tentative identities of other ketocarotenoids were established by chemical evaluation. Seeds from multi-season US and UK field sites maximally accumulated 135 μg/g seed weight of ketocarotenoids, including astaxanthin (47 μg/g seed weight). Although plants had no observable growth reduction, seed size and oil content were reduced in astaxanthin-producing lines. Oil extracted from ketocarotenoid-accumulating seeds showed significantly enhanced oxidative stability and was useful for food oleogel applications.
酮类胡萝卜素，包括虾青素，是由β-胡萝卜素紫罗酮环氧化衍生而来的红色亲脂性色素。这些类胡萝卜素具有卓越的抗氧化能力，作为天然色素具有很高的商业价值，尤其适用于水产养殖饲料，能赋予鲑鱼和虾红色鱼肉。酮类胡萝卜素生物合成途径仅存在于特定的细菌、藻类、真菌和植物物种中，这些物种为生物技术生产酮类胡萝卜素提供了遗传资源。为了优化该途径，我们开发了一个用于酮类胡萝卜素生产的瞬时平台，利用农杆菌将植物（夏侧金盏花）基因、类胡萝卜素β-环4-脱氢酶2（CBFD2）和类胡萝卜素4-羟基-β-环4-脱氢酶（HBFD1），或细菌（短波单胞菌属）基因、β-胡萝卜素酮酶（crtW）和β-胡萝卜素羟化酶（crtZ）导入本氏烟草叶片。在这个测试系统中，与细菌途径相比，植物来源的虾青素途径产生了更高的虾青素产量，且酮类胡萝卜素中间体更少。我们以亚麻荠作为生产平台，评估了植物来源的酮类胡萝卜素生产途径。在种子特异性启动子的控制下，导入了CBFD2和HBFD1基因以及玉米八氢番茄红素合酶基因。与之前对细菌途径的研究不同，我们的策略使β-胡萝卜素几乎完全转化为酮类胡萝卜素，主要包括虾青素。通过化学评估确定了其他酮类胡萝卜素的初步身份。来自美国和英国多季田间试验点的种子最大积累了约135μg/g种子重量的酮类胡萝卜素，包括虾青素（约47μg/g种子重量）。尽管植株没有明显的生长减缓，但生产虾青素的品系种子大小和油含量有所降低。从积累酮类胡萝卜素的种子中提取的油显示出显著增强的氧化稳定性，可用于食品油凝胶应用。
