Because carotenoids act as accessory pigments in photosynthesis, play a key photoprotective role and are of major nutritional importance, carotenogenesis has been a target for crop improvement. Although carotenoids are important precursors of phytohormones, previous genetic manipulations reported little if any effects on biomass production and plant development, but resulted in specific modifications in carotenoid content. Unexpectedly, the expression of the carrot lycopene β‐cyclase (DcLCYB1) in Nicotiana tabacum cv. Xanthi not only resulted in increased carotenoid accumulation, but also in altered plant architecture characterized by longer internodes, faster plant growth, early flowering and increased biomass. Here, we have challenged these transformants with a range of growth conditions to determine the robustness of their phenotype and analyze the underlying mechanisms. Transgenic DcLCYB1 lines showed increased transcript levels of key genes involved in carotenoid, chlorophyll, gibberellin (GA) and abscisic acid (ABA) biosynthesis, but also in photosynthesis‐related genes. Accordingly, their carotenoid, chlorophyll, ABA and GA contents were increased. Hormone application and inhibitor experiments confirmed the key role of altered GA/ABA contents in the growth phenotype. Because the longer internodes reduce shading of mature leaves, induction of leaf senescence was delayed, and mature leaves maintained a high photosynthetic capacity. This increased total plant assimilation, as reflected in higher plant yields under both fully controlled constant and fluctuating light, and in non‐controlled conditions. Furthermore, our data are a warning that engineering of isoprenoid metabolism can cause complex changes in phytohormone homeostasis and therefore plant development, which have not been sufficiently considered in previous studies.

中文翻译：

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通过重新设计植物结构并提高烟草的光合作用效率，致龋基因的表达可以更快地生产生物质。

由于类胡萝卜素在光合作用中起辅助色素的作用，起着关键的光保护作用，并且在营养上具有重要意义，因此类胡萝卜素已成为作物改良的目标。尽管类胡萝卜素是植物激素的重要前体，但以前的基因操作对生物量生产和植物发育的影响很小，甚至没有影响，但导致类胡萝卜素含量发生了特定的改变。出乎意料的是，胡萝卜番茄红素β-环化酶（DcLCYB1）在烟草中的表达。克桑西不仅增加了类胡萝卜素的积累，而且还导致了植物结构的改变，其特征是节间更长，植物生长更快，花期提前和生物量增加。在这里，我们用一系列生长条件挑战了这些转化子，以确定其表型的稳健性并分析了潜在的机制。转基因DcLCYB1品系显示与类胡萝卜素，叶绿素，赤霉素（ABA）和脱落酸（ABA）生物合成有关的关键基因的转录水平升高，但也与光合作用相关基因有关。因此，它们的类胡萝卜素，叶绿素，ABA和GA含量增加。激素应用和抑制剂实验证实了改变的GA / ABA含量在生长表型中的关键作用。由于较长的节间减少了成熟叶片的阴影，因此延迟了叶片衰老的诱导，并且成熟叶片保持了较高的光合能力。在完全受控的恒定光和波动光下以及在非受控条件下，较高的植物产量反映出总植物同化增加。此外，