BACKGROUND Eremophila R.Br. (Scrophulariaceae) is a diverse genus of plants with species distributed across semi-arid and arid Australia. It is an ecologically important genus that also holds cultural significance for many Indigenous Australians who traditionally use several species as sources of medicines. Structurally unusual diterpenoids, particularly serrulatane and viscidane-types, feature prominently in the chemical profile of many species and recent studies indicate that these compounds are responsible for much of the reported bioactivity. We have investigated the biosynthesis of diterpenoids in three species: Eremophila lucida, Eremophila drummondii and Eremophila denticulata subsp. trisulcata. RESULTS In all studied species diterpenoids were localised to the leaf surface and associated with the occurrence of glandular trichomes. Trichome-enriched transcriptome databases were generated and mined for candidate terpene synthases (TPS). Four TPSs with diterpene biosynthesis activity were identified: ElTPS31 and ElTPS3 from E. lucida were found to produce (3Z,7Z,11Z)-cembratrien-15-ol and 5-hydroxyviscidane, respectively, and EdTPS22 and EdtTPS4, from E. drummondii and E. denticulata subsp. trisulcata, respectively, were found to produce 8,9-dihydroserrulat-14-ene which readily aromatized to serrulat-14-ene. In all cases, the identified TPSs used the cisoid substrate, nerylneryl diphosphate (NNPP), to form the observed products. Subsequently, cis-prenyl transferases (CPTs) capable of making NNPP were identified in each species. CONCLUSIONS We have elucidated two biosynthetic steps towards three of the major diterpene backbones found in this genus. Serrulatane and viscidane-type diterpenoids are promising candidates for new drug leads. The identification of an enzymatic route to their synthesis opens up the possibility of biotechnological production, making accessible a ready source of scaffolds for further modification and bioactivity testing.

中文翻译：

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神经磷酸二磷酸神经甘油酯是嗜油菌属物种中的异戊二烯，粘稠烷和西门烷型二萜的前体。

背景嗜血杆菌R.Br. （玄参科）是植物的一个属，其物种分布在半干旱和干旱的澳大利亚。对于许多传统上使用几种物种作为药物来源的澳大利亚土著人来说，它是一个重要的生态属，也具有文化意义。结构上不常见的二萜类化合物，尤其是斯鲁拉丹烷和内脏烷型，在许多物种的化学特征中都非常突出，最近的研究表明，这些化合物是许多报道的生物活性的原因。我们已经研究了三种生物中二萜的生物合成：灵芝Eeremophila lucida，德拉蒙德Eermophila drummondii和齿叶Eremophila denticulata亚种。Trisulcata。结果在所有研究的物种中，二萜类化合物局限于叶片表面，并与腺毛发生有关。生成富集丰富的转录组的转录组数据库，并为候选萜合酶（TPS）进行挖掘。鉴定出四个具有二萜生物合成活性的TPS：发现来自E. lucida的ElTPS31和ElTPS3分别产生（3Z，7Z，11Z）-cembratrien-15-ol和5-hydroxyviscidane，以及来自E. drummondii和EdTPS22和EtTPS4。 E. denticulata亚种 分别发现trisulcata生产8,9-dihydroserrulat-14-ene，它容易芳香化为serrulat-14-ene。在所有情况下，鉴定出的TPS均使用类固醇底物二磷酸神经烷基酯（NNPP）形成观察到的产物。随后，在每个物种中鉴定出能够制造NNPP的顺式异戊二烯基转移酶（CPT）。结论我们已经阐明了针对该属中三个主要的二萜骨架的两个生物合成步骤。Serrulatane和viscidane型二萜类化合物有望成为新药的候选药物。酶促合成途径的鉴定开辟了生物技术生产的可能性，为进一步修饰和生物活性测试提供了现成的支架来源。