NgLst8 Coactivates TOR Signaling to Activate Photosynthetic Growth in Nannochloropsis gaditana

The target of rapamycin (TOR) serves as a central regulator of cell growth, coordinating anabolic and catabolic processes in response to nutrient availability, growth factors, and energy supply. Activation of TOR has been shown to promote photosynthesis, growth, and development in yeast, animals, and plants. In this study, the complete cDNA sequence of the <i>Lst8</i> gene was obtained from <i>Nannochloropsis gaditana</i>. The structure of <i>N. gaditana</i> LST8 comprises a typical WD40 repeat sequence, exhibiting high sequence similarity to several known LST8 proteins. By overexpressing the <i>Lst8</i> gene in <i>N. gaditana</i>, we constructed the NgLst8 transgenic algal strain and measured its photosynthetic activity and growth. We observed that an increase in LST8 abundance promotes the expression of TOR-related kinase, thereby enhancing photosynthetic growth. Transcriptome analysis further elucidated the response mechanism of elevated <i>Lst8</i> abundance in relation to photosynthesis. Our findings indicate that increased <i>Lst8</i> expression activates ABC transporter proteins and the MAPK signaling pathway, which regulate the transmembrane transport of sugars and other metabolites, integrate photosynthesis, sugar metabolism, and energy signaling, and modulate energy metabolism in algal cells through interactions with the TOR signaling pathway.