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Photosynthetic microalgae likeNannochloropsishold enormous potential as sustainable, light‐driven biofactories for the production of high‐value natural products such as terpenoids.Nannochloropsis oceanicais distinguished as a particularly robust host with extensive genomic and transgenic resources available. Its capacity to grow in wastewater, brackish, and sea waters, coupled with advances in microalgal metabolic engineering, genome editing, and synthetic biology, provides an excellent opportunity. In the present work, we demonstrate howN. oceanicacan be engineered to produce the diterpene casbene—an important intermediate in the biosynthesis of pharmacologically relevant macrocyclic diterpenoids. Casbene accumulated after stably expressing and targeting the casbene synthase fromDaphne genkwa(DgTPS1) to the algal chloroplast. The engineered strains yielded production titers of up to 0.12 mg g⁻¹total dry cell weight (DCW) casbene. Heterologous overexpression and chloroplast targeting of two upstream rate‐limiting enzymes in the 2‐C‐methyl‐d‐erythritol 4‐phosphate pathway,Coleus forskohlii1‐deoxy‐d‐xylulose‐5‐phosphate synthase and geranylgeranyl diphosphate synthase genes, further enhanced the yield of casbene to a titer up to 1.80 mg g⁻¹DCW. The results presented here form a basis for further development and production of complex plant diterpenoids in microalgae.

Circadian clocks allow organisms to predict environmental changes caused by the rotation of the Earth. Although circadian rhythms are widespread among different taxa, the core components of circadian oscillators are not conserved and differ between bacteria, plants, animals and fungi. Stramenopiles are a large group of organisms in which circadian rhythms have been only poorly characterized and no clock components have been identified. We have investigated cell division and molecular rhythms inNannochloropsisspecies. In the four strains tested, cell division occurred principally during the night period under diel conditions; however, these rhythms damped within 2–3 days after transfer to constant light. We developed firefly luciferase reporters for the long‐term monitoring ofin vivotranscriptional rhythms in twoNannochlropsisspecies,Nannochloropsis oceanicaCCMP1779 andNannochloropsis salinaCCMP537. The reporter lines express anticipatory behavior under light/dark cycles and free‐running bioluminescence rhythms with periods of ~21–31 h that damped within ~3–4 days under constant light. Using different entrainment regimes, we demonstrate that these rhythms are modulated by a circadian‐type oscillator. In addition, the phase of free‐running luminescence rhythms can be modulated pharmacologically using aCK1 ε/δ inhibitor, suggesting a role of this kinase in theNannochloropsisclock. Together with the molecular and genomic tools available forNannochloropsisspecies, these reporter lines represent an excellent system for future studies on the molecular mechanisms of stramenopile circadian oscillators.