SummaryBuilding sustainable platforms to produce biofuels and specialty chemicals has become an increasingly important strategy to supplement and replace fossil fuels and petrochemical‐derived products. Terpenoids are the most diverse class of natural products that have many commercial roles as specialty chemicals. Poplar is a fast growing, biomassdense bioenergy crop with many species known to produce large amounts of the hemiterpene isoprene, suggesting an inherent capacity to produce significant quantities of other terpenes. Here we aimed to engineer poplar with optimized pathways to produce squalene, a triterpene commonly used in cosmetic oils, a potential biofuel candidate, and the precursor to the further diversified classes of triterpenoids and sterols. The squalene production pathways were either re‐targeted from the cytosol to plastids or co‐produced with lipid droplets in the cytosol. Squalene and lipid droplet co‐production appeared to be toxic, which we hypothesize to be due to disruption of adventitious root formation, suggesting a need for tissue specific production. Plastidial squalene production enabled up to 0.63 mg/g fresh weight in leaf tissue, which also resulted in reductions in isoprene emission and photosynthesis. These results were also studied through a technoeconomic analysis, providing further insight into developing poplar as a production host.

中文翻译：

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用于生物生产三萜角鲨烯的工程杨树

摘要建立可持续平台来生产生物燃料和特种化学品已成为补充和替代化石燃料和石化衍生产品的日益重要的战略。萜类化合物是最多样化的天然产物，作为特种化学品具有许多商业作用。杨树是一种生长快速、生物量密集的生物能源作物，已知许多物种能够产生大量的半萜异戊二烯，这表明杨树具有产生大量其他萜烯的内在能力。在这里，我们的目标是通过优化的途径来设计杨树来生产角鲨烯，角鲨烯是一种常用于化妆品油的三萜烯，是一种潜在的生物燃料候选者，也是进一步多样化的三萜类化合物和甾醇类的前体。角鲨烯生产途径要么从细胞质重新定位到质体，要么与细胞质中的脂滴共同产生。角鲨烯和脂滴的共同生产似乎是有毒的，我们假设这是由于不定根形成的破坏，这表明需要组织特异性生产。质体角鲨烯的产生使叶组织的鲜重达到 0.63 mg/g，这也导致异戊二烯排放和光合作用减少。还通过技术经济分析对这些结果进行了研究，为开发杨树作为生产宿主提供了进一步的见解。