A nitrogen-deprivation-activated gene promotes oil production in an oleaginous microalga Nannochloropsis oceanica

Oleaginous microalgae such as Nannochloropsis oceanica are well known for their ability to accumulate substantial amounts of lipids (including triacylglycerols (TAGs) and high-value fatty acids) particularly under nitrogen deprivation (ND). However, the molecular mechanisms governing ND-induced lipid remodeling in microalgae remain insufficiently characterized. In this study, we identified an α-protein kinase, NoS1P, through transcriptomic comparison of nitrogen-replete and ND conditions in N. oceanica . Sequence analysis revealed that NoS1P generates two mRNA isoforms, NoS1Pshort and NoS1Plong , from a single gene. Functional characterization showed that loss of NoS1P impaired growth, photosynthetic performance, and lipid accumulation under ND, whereas overexpression of NoS1P markedly enhanced the production of total lipid, TAG, palmitic and palmitoleic acids. These results demonstrate that NoS1P is a key regulator of nitrogen-responsive lipid biosynthesis in N. oceanica . Beyond advancing understanding of microalgal stress-responsive metabolism, this work provides a molecular basis for improving the yield of high-value nutritional lipids, supporting the use of Nannochloropsis as a promising platform for nutraceutical and functional feed applications. • NoS1P is strongly induced by nitrogen deprivation in N. oceanica . • Knockout of NoS1P reduces growth, photosynthesis, and lipid production. • Overexpressing NoS1P boosts oil, TAG, and fatty acid accumulation. • Two NoS1P isoforms show distinct stress-response expression patterns. • Co-overexpression of both isoforms yields the highest lipid increase.