State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Sciences, South China Agricultural University, Guangzhou 510642, China.
State Key Laboratory for Conservation and Utilization of Subtropical Agro-Bioresources, College of Life Sciences, South China Agricultural University, Guangzhou 510642, China.
Mol Plant. 2018 Dec 3;11(12):1440-1448. doi: 10.1016/j.molp.2018.09.007. Epub 2018 Oct 6.
Carotenoids are important phytonutrients with antioxidant properties, and are widely used in foods and feedstuffs as supplements. Astaxanthin, a red-colored ketocarotenoid, has strong antioxidant activity and thus can benefit human health. However, astaxanthin is not produced in most higher plants. Here we report the bioengineering of astaxanthin biosynthesis in rice endosperm by introducing four synthetic genes, sZmPSY1, sPaCrtI, sCrBKT, and sHpBHY, which encode the enzymes phytoene synthase, phytoene desaturase, β-carotene ketolase, and β-carotene hydroxylase, respectively. Transgneic overexpression of two (sZmPSY1 and sPaCrtI), three (sZmPSY1, sPaCrtI and sCrBKT), and all these four genes driven by rice endosperm-specific promoters established the carotenoid/ketocarotenoid/astaxanthin biosynthetic pathways in the endosperm and thus resulted in various types of germplasm, from the yellow-grained β-carotene-enriched Golden Rice to orange-red-grained Canthaxanthin Rice and Astaxanthin Rice, respectively. Grains of Astaxanthin Rice were enriched with astaxanthin in the endosperm and had higher antioxidant activity. These results proved that introduction of a minimal set of four transgenes enables de novo biosynthesis of astaxanthin in the rice endosperm. This work provides a successful example for synthetic biology in plants and biofortification in crops; the biofortified rice products generated by this study could be consumed as health-promoting foods and processed to produce dietary supplements.
类胡萝卜素是具有抗氧化特性的重要植物营养素，广泛用作食品和饲料添加剂。虾青素是一种红色酮类类胡萝卜素，具有很强的抗氧化活性，因此有益于人类健康。然而，虾青素在大多数高等植物中并不产生。在这里，我们通过引入四个合成基因 sZmPSY1、sPaCrtI、sCrBKT 和 sHpBHY，报告了在水稻胚乳中生物工程虾青素生物合成的方法，这些基因分别编码八氢番茄红素合酶、八氢番茄红素去饱和酶、β-胡萝卜素酮化酶和 β-胡萝卜素羟化酶。两个（sZmPSY1 和 sPaCrtI）、三个（sZmPSY1、sPaCrtI 和 sCrBKT）和所有四个基因的转基因过量表达，这些基因都由水稻胚乳特异性启动子驱动，在胚乳中建立了类胡萝卜素/酮类胡萝卜素/虾青素生物合成途径，从而产生了不同类型的种质，从富含β-胡萝卜素的黄粒 Golden Rice 到橙红色粒的角黄素 Rice 和虾青素 Rice。虾青素 Rice 的胚乳富含虾青素，具有更高的抗氧化活性。这些结果证明，引入一组最少的四个转基因可以在水稻胚乳中从头合成虾青素。这项工作为植物合成生物学和作物生物强化提供了一个成功的范例；本研究产生的生物强化水稻产品可以作为促进健康的食品消费，并加工成膳食补充剂。
