Chuang Ling, Liu Shenyu, Biedermann Dave, Franke Jakob
Centre of Biomolecular Drug Research, Leibniz University Hannover, Hanover, Germany.
Institute of Botany, Leibniz University Hannover, Hanover, Germany.
Front Plant Sci. 2022 Aug 23;13:958138. doi: 10.3389/fpls.2022.958138. eCollection 2022.
The tree of heaven, (MILL.) SWINGLE, is a globally invasive plant known to secrete allelopathic metabolites called quassinoids. Quassinoids are highly modified triterpenoids. So far, nothing has been known about the biochemical basis of quassinoid biosynthesis. Here, based on transcriptome and metabolome data of , we present the first three steps of quassinoid biosynthesis, which are catalysed by an oxidosqualene cyclase and two cytochrome P450 monooxygenases, resulting in the formation of the protolimonoid melianol. Strikingly, these steps are identical to the first steps of the biosynthesis of limonoids, structurally different triterpenoids from sister plant families within the same order Sapindales. Our results are therefore not only important to fully understand the biosynthesis of complex triterpenoids in plants, but also confirm the long-standing hypothesis that quassinoids and limonoids share an evolutionary origin. In addition, our transcriptome data for will be beneficial to other researchers investigating the physiology and ecology of this invasive tree.
臭椿（樗树）（Ailanthus altissima (MILL.) SWINGLE）是一种全球范围内具有入侵性的植物，已知其会分泌称为苦木素类的化感代谢产物。苦木素类是高度修饰的三萜类化合物。到目前为止，关于苦木素类生物合成的生化基础尚不清楚。在此，基于臭椿的转录组和代谢组数据，我们展示了苦木素类生物合成的前三个步骤，这三个步骤由一种氧化鲨烯环化酶和两种细胞色素P450单加氧酶催化，最终形成原柠檬苦素类化合物米仔兰醇。引人注目的是，这些步骤与柠檬苦素类化合物生物合成的第一步相同，柠檬苦素类是来自同一目无患子目内姐妹植物科的结构不同的三萜类化合物。因此，我们的结果不仅对于全面理解植物中复杂三萜类化合物的生物合成很重要，而且证实了长期以来的假说，即苦木素类和柠檬苦素类具有共同的进化起源。此外，我们的臭椿转录组数据将有助于其他研究这种入侵树木生理学和生态学的研究人员。
