Department of Plant and Environmental Sciences, University of Copenhagen, Thorvaldsensvej 40, Frederiksberg C, 1871, Denmark.
Department of Biology, University of Crete, PO Box 2208, Heraklion, 71003, Greece.
New Phytol. 2019 Apr;222(1):230-243. doi: 10.1111/nph.15586. Epub 2018 Dec 10.
Diatoms are eukaryotic, unicellular algae that are responsible for c. 20% of the Earth's primary production. Their dominance and success in contemporary oceans have prompted investigations on their distinctive metabolism and physiology. One metabolic pathway that remains largely unexplored in diatoms is isoprenoid biosynthesis, which is responsible for the production of numerous molecules with unique features. We selected the diatom species Haslea ostrearia because of its characteristic isoprenoid content and carried out a comprehensive transcriptomic analysis and functional characterization of the genes identified. We functionally characterized one farnesyl diphosphate synthase, two geranylgeranyl diphosphate synthases, one short-chain polyprenyl synthase, one bifunctional isopentenyl diphosphate isomerase - squalene synthase, and one phytoene synthase. We inferred the phylogenetic origin of these genes and used a combination of functional analysis and subcellular localization predictions to propose their physiological roles. Our results provide insight into isoprenoid biosynthesis in H. ostrearia and propose a model of the central steps of the pathway. This model will facilitate the study of metabolic pathways of important isoprenoids in diatoms, including carotenoids, sterols and highly branched isoprenoids.
硅藻是真核单细胞藻类，其光合作用约占地球初级生产力的 20%。它们在当代海洋中的优势和成功促使人们对其独特的代谢和生理机能进行了研究。硅藻中一种代谢途径——异戊烯基生物合成，其负责生成具有独特特征的众多分子，但目前仍在很大程度上尚未被探索。我们选择了具有特征性异戊烯基含量的硅藻物种 Haslea ostrearia，并对鉴定出的基因进行了全面的转录组分析和功能特征分析。我们对一个法呢基二磷酸合酶、两个牻牛儿基牻牛儿基二磷酸合酶、一个短链多萜烯合酶、一个双功能异戊烯二磷酸异构酶-鲨烯合酶和一个八氢番茄红素合酶进行了功能特征分析。我们推断了这些基因的系统发育起源，并结合功能分析和亚细胞定位预测，提出了它们的生理作用。我们的研究结果为 H.ostrearia 的异戊烯基生物合成提供了深入的了解，并提出了该途径中心步骤的模型。该模型将有助于研究硅藻中重要异戊烯基的代谢途径，包括类胡萝卜素、固醇和高度支化的异戊烯基。
