Improving lipid productivity by engineering a control-knob gene in the oleaginous microalga Nannochloropsis oceanica

Nannochloropsis spp. are promising industrial microalgae for scalable oil production and the lipid production can be boosted by nutrient starvation and high irradiance. However, these stimuli halt growth, thereby decreasing overall productivity. In this study, we created transgenic N. oceanica where AtDXS gene encoding 1-deoxy-D-xylulose 5-phosphate synthase (DXS) derived from Arabidopsis thaliana was overexpressed in vivo. Compared with the wild type (WT), engineered Nannochloropsis showed a higher CO₂ absorption capacity and produced more biomass, lipids, and carbohydrates with more robust growth in either preferred conditions or various stressed conditions (low light, high light, nitrogen starvation, and trace element depletion). Specifically, relative to the WT, lipid production increased by ~68.6% in nitrogen depletion (~1.08 ​g ​L^-1) and ~110.6% in high light (~1.15 ​g ​L^-1) in the transgenic strains. As for neutral lipid (triacylglycerol, TAG), the engineered strains produced ~93.2% more in nitrogen depletion (~0.77 ​g ​L^-1) and ~148.6% more in high light (~0.80 ​g ​L^-1) than the WT. These values exceed available records in engineered industrial microalgae. Therefore, engineering control-knob genes could modify multiple biological processes simultaneously and enable efficient carbon partitioning to lipid biosynthesis with elevated biomass productivity. It could be further exploited for simultaneous enhancement of growth property and oil productivity in more industrial microalgae.