Combined transcriptomic and proteomic analysis reveals the influence of sulfur availability on nitrogen and carbon metabolism and lipid accumulation in Tribonema minus (Xanthophyceae)

Compared with single-cell microalgae, the filamentous microalgae Tribonema have stronger anti-predation ability and can be harvested more easily during large-scale production. To evaluate the potential of Tribonema as a raw material for biodiesel and bioproducts, this study conducted the comprehensive analysis of the biomass concentration and total lipid accumulation patterns of 12 Tribonema strains under nitrogen (N) and sulfur (S) nutritional regulation. Furthermore, by integrating multi-omics technologies, this study elucidated the potential mechanisms underlying lipid metabolism in T. minus under S-stress conditions. The results showed that under N concentration treatments (0, 3, and 18 mM), the biomass concentration of all 12 Tribonema strains initially increased and then decreased with increasing N concentration, while the total lipid content showed no significant correlation with N concentration. Under S concentration treatments (0, 0.3, and 1.2 mM), the biomass of all Tribonema species significantly increased with increasing S concentration. The total lipid and fatty acid content peaked at the lowest S concentration. A combined transcriptomic and proteomic analysis in T. minus revealed that under S-deficient conditions, the expression of genes and proteins related to N metabolism (e.g., nitrate reductase and nitrite reductase) was downregulated, and those related to S metabolism (e.g., ATP sulfurylase and APS kinase) were upregulated, thereby balancing intracellular levels of N and S to maintain normal growth and metabolism. The genes and proteins encoding the rate-limiting enzymes in the glycolysis pathway were upregulated, promoting pyruvate synthesis. The expression of genes and proteins associated with lipid synthesis (e.g., DGAT and PDAT) was significantly upregulated, thereby promoting the accumulation of lipids. This study demonstrated that the regulation of S availability significantly impacts the metabolic network of Tribonema, providing theoretical support for its application in biodiesel and other high-value bioproducts.