Zhejiang Provincial Key Laboratory of Biotechnology on Specialty Economic Plants, Zhejiang Normal University, Jinhua 321004, Zhejiang, China.
Department of Environmental Engineering, Quzhou University, Quzhou 324000, Zhejiang, China.
J Agric Food Chem. 2020 Oct 14;68(41):11503-11511. doi: 10.1021/acs.jafc.0c03092. Epub 2020 Sep 30.
Lycopene is the most potent antioxidant among all carotenoids and is beneficial to human health. A ripe fruit of autumn olive ( Thunb.) accumulates a high level of lycopene, which is 5-20 times higher than that in an ordinary tomato fruit. During fruit ripening of autumn olive, only phytoene synthase () expression pattern shows a tight positive correlation with the increased lycopene content observed at four ripening stages, while the lycopene ε-cyclase () transcript could not be detected throughout fruit ripening. Here, we investigated whether the two genes are important targets for engineering lycopene biosynthesis. The full-length cDNAs of and were first isolated. Fruit-specific overexpression of in tomato fruits resulted in elevated contents of lycopene and β-carotene through feedforward regulation of carotenogenic genes, i.e., downregulation of and upregulation of and . These fruits were decreased in ethylene production throughout ripening. Transcript levels of genes for system-2 ethylene synthesis (2, 4, 1, and 3), perception (3 and 4), and response (4 and 8) were also inhibited in -overexpressing fruits. Repressing ethylene synthesis and signaling transduction delayed fruit climacteric ripening of transgenic tomato plants. Additionally, RNAi suppression of enhanced β-carotene but not lycopene accumulation through altered expression of carotenogenic genes in transgenic tomato fruits by both feedforward and feedback regulatory mechanisms. Ethylene production in -RNAi fruits decreased, thereby delaying fruit ripening. Collectively, these results confirmed that transcriptional regulation of and plays a crucial role and a part in massive lycopene accumulation in autumn olive fruits, respectively. overexpression enhanced lycopene accumulation in tomato fruits independently of the ethylene pathway but did not influence the size and weight of tomato fruits. can be used as an effective strategy capable of elevating the lycopene content in fruits for improving quality.
番茄红素是所有类胡萝卜素中最有效的抗氧化剂，对人体健康有益。秋橄榄（Thunb.）的成熟果实积累了高水平的番茄红素，是普通番茄果实的 5-20 倍。在秋橄榄果实成熟过程中，只有八氢番茄红素合酶（）表达模式与在四个成熟阶段观察到的番茄红素含量增加呈紧密正相关，而番茄红素 ε-环化酶（）转录本在整个果实成熟过程中都无法检测到。在这里，我们研究了这两个基因是否是工程番茄红素生物合成的重要靶点。首先分离了和的全长 cDNA。在番茄果实中特异性过表达，通过对类胡萝卜素生物合成基因的反馈调节，导致番茄红素和β-胡萝卜素含量升高，即下调和上调和。这些果实整个成熟过程中乙烯生成量减少。系统 2 乙烯合成（2、4、1 和 3）、感知（3 和 4）和响应（4 和 8）基因的转录水平也在过表达果实中受到抑制。抑制乙烯合成和信号转导通过改变过表达番茄植物中类胡萝卜素生物合成基因的表达，延迟了转基因番茄果实的呼吸跃变成熟。此外，通过反馈和前馈调节机制，抑制的 RNAi 增强了β-胡萝卜素但没有番茄红素的积累，改变了转基因番茄果实中类胡萝卜素生物合成基因的表达。-RNAi 果实中的乙烯产量下降，从而延迟果实成熟。总之，这些结果证实了和的转录调控分别在秋橄榄果实中番茄红素的大量积累中起着关键作用。过表达增强了番茄果实中番茄红素的积累，独立于乙烯途径，但不影响番茄果实的大小和重量。可以作为一种有效策略，提高果实中的番茄红素含量，改善品质。
