Li Zhenjun, Gao Jianjie, Wang Bo, Xu Jing, Fu Xiaoyan, Han Hongjuan, Wang Lijuan, Zhang Wenhui, Deng Yongdong, Wang Yu, Gong Zehao, Tian Yongsheng, Peng Rihe, Yao Quanhong
Shanghai Key Laboratory of Agricultural Genetics and Breeding, Agro-Biotechnology Research Institute, Shanghai Academy of Agricultural Sciences, Shanghai, China.
Front Plant Sci. 2022 Jul 15;13:951605. doi: 10.3389/fpls.2022.951605. eCollection 2022.
Carotenoids, indispensable isoprenoid phytonutrients, are synthesized in plastids and are known to be deficient in rice endosperm. Many studies, involving transgenic manipulations of carotenoid biosynthetic genes, have been performed to obtain carotenoid-enriched rice grains. Nuclear-encoded GOLDEN2-LIKE (GLK) transcription factors play important roles in the regulation of plastid and thylakoid grana development. Here, we show that endosperm-specific overexpression of rice gene () leads to enhanced carotenoid production, increased grain yield, but deteriorated grain quality in rice. Subsequently, we performed the bioengineering of carotenoids biosynthesis in rice endosperm by introducing other three carotenogenic genes, , , and , which encode the enzymes truncated 3-hydroxy-3-methylglutaryl-CoA reductase, phytoene synthase, and phytoene desaturase, respectively. Transgenic overexpression of all four genes (, , , and ) driven by rice endosperm-specific promoter established a mini carotenoid biosynthetic pathway in the endosperm and exerted a roughly multiplicative effect on the carotenoid accumulation as compared with the overexpression of only three genes (, , and ). In addition, the yield enhancement and quality reduction traits were also present in the transgenic rice overexpressing the selected four genes. Our results revealed that confers favorable characters in rice endosperm and could help to refine strategies for the carotenoid and other plastid-synthesized micronutrient fortification in bioengineered plants.
类胡萝卜素是不可或缺的类异戊二烯植物营养素，在质体中合成，且已知在水稻胚乳中缺乏。许多涉及类胡萝卜素生物合成基因转基因操作的研究已开展，旨在获得富含类胡萝卜素的水稻籽粒。核编码的类GOLDEN2转录因子（GLK）在质体和类囊体基粒发育的调控中发挥重要作用。在此，我们表明水稻基因（）在胚乳中特异性过表达会导致类胡萝卜素产量增加、谷物产量提高，但水稻籽粒品质下降。随后，我们通过导入另外三个类胡萝卜素生成基因，即、和，在水稻胚乳中进行类胡萝卜素生物合成的生物工程改造，这三个基因分别编码截短的3-羟基-3-甲基戊二酰辅酶A还原酶、八氢番茄红素合酶和八氢番茄红素去饱和酶。由水稻胚乳特异性启动子驱动的所有四个基因（、、、）的转基因过表达在胚乳中建立了一条微型类胡萝卜素生物合成途径，与仅过表达三个基因（、、）相比，对类胡萝卜素积累产生了大致相乘的效应。此外，过表达所选四个基因的转基因水稻中也存在产量增加和品质降低的性状。我们的结果表明，赋予了水稻胚乳良好的特性，并有助于完善生物工程植物中类胡萝卜素和其他质体合成的微量营养素强化策略。
