Proteomic insights into cell signaling and stress response mechanisms in Chaetoceros muelleri under nitrogen...

Microalgae are often called "green factories" because they can perform photosynthesis, converting sunlight into biomass and high-value metabolites. Nitrogen concentration is a critical factor influencing protein accumulation. Unfortunately, nitrogen deprivation often negatively impacts biomass production. Understanding the relationship between nitrogen concentration and protein accumulation is crucial for harnessing the potential of microalgae in various industries and addressing environmental challenges. Here, we quantitatively compared the proteomic profiles of Chaetoceros muelleri diatom, grown in two Nitrogen-deficient conditions and control treatment by employing a Tandem Mass Tag-based quantitative proteomic approach. Proteins involved in photosynthesis were differentially accumulated under moderately nitrogen-deficient conditions. In contrast, proteins involved in cell signaling and protection mechanisms were differentially accumulated under severely nitrogen-limited conditions. Proteins associated with nitrogen metabolism, carbohydrate metabolism, and protein biosynthesis were differentially decreased in severely nitrogen-limited conditions, indicating differential response mechanisms of C. muelleri to varying nitrogen conditions. Our results show that C. muelleri employs distinct strategies in response to nitrogen limitation. These results provide valuable insights into the adaptive strategies of C. muelleri under nitrogen limitation, offering potential applications in optimizing microalgal cultures for the enhanced production of target metabolites in industrial bioreactors. BIOLOGICAL SIGNIFICANCE: The marine diatom Chaetoceros muelleri accumulates lipids and carbohydrates under low nitrogen conditions without affecting its biomass. Response to nitrogen limitation in C. muelleri was examined by isobaric labelling-based proteomics. We identified changes mainly focused on photosynthesis pathways, cell signaling and protection mechanisms, nitrogen and carbohydrate metabolism, as well as protein biosynthesis. Our results indicate that C. muelleri activate unique strategies in response to different nitrogen concentrations, and this differential response represents a key factor for inducing metabolite accumulation without affecting biomass production.