Transcriptional reprogramming of intermediate metabolism gene induced by Phosphatidylinositol 3-Kinase in Phaeodactylum tricornutum

Phosphatidylinositol 3-kinase and its product phosphatidylinositol 3-phosphate play a key role in phospholipid and energy metabolism, protein traffic and exocytosis. However, the role of phosphatidylinositol 3-kinase on lipid production in Phaeodactylum tricornutum is still unclear. Phosphatidylinositol 3-kinase in Phaeodactylum tricornutum is more closely associated with homologs from mammals than higher plants. Here, we use pharmacological, transcriptome, and biochemical approaches to reveal that phosphatidylinositol 3-kinase signaling was involved in lipid accumulation. For investigating the role of phosphatidylinositol 3-kinase in Phaeodactylum tricornutum, phosphatidylinositol 3-kinase inhibitors, wortmannin and LY294002, were used. Fluorescein diacetate fluorescence analysis showed that 1 μM wortmannin and 1 μM LY294002 had no significant effect on cellular viability. Treatment with phosphatidylinositol 3-kinase inhibitors increased triacylglycerols production and the ratio of saturation fatty acid but extended the logarithmic phase of the cells. Metabolite content analysis showed that total content of soluble proteins was decreased, whereas the total lipids content and carbohydrates content were remarkably increased under phosphatidylinositol 3-kinase inhibitors treatment. RNA-Seq analysis showed the expression of genes involved in starch and sucrose metabolism, nitrogen and amino acid metabolism were upregulated while that in pigment metabolism, RNA metabolism were downregulated under wortmannin treatment in standard condition. The pathway induced by wortmannin under nitrogen deprivation conditions seems to be different in standard conditions. The expression of gene involved in RNA metabolism and MAPK signaling was upregulated while that in lipid metabolism was decreased under wortmannin treatment in N-free culture. This study demonstrated a role of phosphatidylinositol 3-kinase in the allocation of carbon and reductant towards lipids in Phaeodactylum tricornutum.