Terpenoids are of great interests in a broad range of health-beneficial biological activities and various industrial applications. In plants, terpenoids are synthesized by two distinct pathways, methylerythritol phosphate (MEP) and mevalonate pathways in a separate location. MEP pathway supplies isoprene precursors isopentenyl diphosphate (IPP) and its isomer dimethylallyl diphosphate (DMAPP) of terpenoid biosynthesis in plant plastids. The MEP pathway has been an engineering target to increase the metabolic flux towards higher terpenoid production in plants. 1-Hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate reductase (HDR) is the terminal step of the MEP pathway to regulate the terpenoid biosynthesis and is encoded by three paralogous genes in Ginkgo biloba. In this study, we assessed the effect of overexpression of GbHDR1 on terpenoid metabolism in poplar plants. Overexpression of GbHDR1 in poplar plants accelerated growth and delayed winter-bud formation. Transcript levels of gibberellin, chlorophylls, and carotenoid biosynthetic genes in GbHDR1-overexpressing (GbHDR1ox) poplars were up-regulated, suggesting metabolic flux enhancement. Moreover, enhanced contents of chlorophylls and carotenoids in the leaves of the GbHDR1ox plants resulted in a higher photosynthetic rate as a consequence. Therefore, we expect the GbHDR1 overexpression will be a desirable engineering point of the MEP pathway for enhancing terpenoid metabolic flux and production in plants.

中文翻译：

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杨树银杏叶 1-Hydroxy-2-methyl-2-(E)-butenyl 4-diphosphate Reductase 1 (GbHDR1) 基因过表达增强磷酸甲基赤藓糖醇 (MEP) 通路的代谢通量

萜类化合物在广泛的有益健康的生物活性和各种工业应用中具有重要意义。在植物中，萜类化合物是通过两种不同的途径合成的，甲基赤藓糖醇磷酸盐 (MEP) 和甲羟戊酸途径在不同的位置。MEP 途径提供植物质体中萜类生物合成的异戊二烯前体异戊烯基二磷酸 (IPP) 及其异构体二甲基烯丙基二磷酸 (DMAPP)。MEP 途径一直是增加植物代谢通量以提高萜类化合物产量的工程目标。1-Hydroxy-2-methyl-2-(E)-butenyl-4-diphosphate reductase (HDR) 是 MEP 通路调节萜类生物合成的最后一步，由银杏叶中的三个旁系同源基因编码。在这项研究中，我们评估了 GbHDR1 过表达对杨树中萜类化合物代谢的影响。杨树中 GbHDR1 的过表达加速了生长并延迟了冬芽的形成。GbHDR1 过表达 (GbHDR1ox) 杨树中赤霉素、叶绿素和类胡萝卜素生物合成基因的转录水平上调，表明代谢通量增强。此外，GbHDR1ox 植物叶片中叶绿素和类胡萝卜素含量的增加导致更高的光合速率。因此，我们预计 GbHDR1 过表达将成为 MEP 途径的理想工程点，用于增强植物中的萜类化合物代谢通量和产量。GbHDR1 过表达 (GbHDR1ox) 杨树中的类胡萝卜素生物合成基因上调，表明代谢通量增强。此外，GbHDR1ox 植物叶片中叶绿素和类胡萝卜素含量的增加导致更高的光合速率。因此，我们预计 GbHDR1 过表达将成为 MEP 途径的理想工程点，用于增强植物中的萜类化合物代谢通量和产量。GbHDR1 过表达 (GbHDR1ox) 杨树中的类胡萝卜素生物合成基因上调，表明代谢通量增强。此外，GbHDR1ox 植物叶片中叶绿素和类胡萝卜素含量的增加导致更高的光合速率。因此，我们预计 GbHDR1 过表达将成为 MEP 途径的理想工程点，用于增强植物中的萜类化合物代谢通量和产量。