Target of Rapamycin is a crucial regulator of photosynthesis and nutrient metabolism partitioning in Nannochloropsis gaditana

Utilizing microalgae as "photosynthetic cell factories" for compound production holds significant potential for sustainable carbon neutrality. However, the inherent inefficiency of algal photosynthesis, a limiting factor for productivity, represents a critical area for enhancement. Among the key regulatory mechanisms, the Target of Rapamycin (TOR), essential for cell growth regulation and known for its conserved structure across eukaryotes, remains underexplored in Nannochloropsis gaditana. In this study, we identified conserved component of the TOR complex in N. gaditana. Rapamycin (RAP) effectively inhibited photosynthetic growth and enhanced lipid accumulation in N. gaditana, as demonstrated by sensitivity tests. Transcriptomic analysis revealed that NgTOR modulates multiple intracellular metabolic and signaling pathways. Specifically, genes associated with photosynthesis and chlorophyll synthesis were significantly down-regulated following NgTOR inhibition. Additionally, genes involved in carbon metabolism, the TCA cycle, and amino acid biosynthesis were markedly reduced, while those related to lipid metabolism were up-regulated, resulting in stunted cell growth and increased lipid accumulation. Furthermore, blocking photosynthesis with DCMU significantly reduced the transcriptional activity of TOR-related complexes, highlighting a bidirectional regulatory interaction. These findings underscore the pivotal role of the TOR signaling pathway in regulating photosynthesis, carbon metabolism, and lipid metabolism in N. gaditana, setting the stage for further studies on photosynthetic autotrophy and lipid metabolic pathways in this species.