Determining metabolic mechanism linking phospholipids and docosahexaenoic acid through phosphatidylcholine synthesis by phosphocholine cytidylyltransferase (CCT) overexpression in Schizochytrium sp.

The polyunsaturated fatty acid (PUFA) metabolism of Schizochytrium, an excellent oil-producing microorganism, is closely related to phosphatidylcholine (PC) synthesis, which favors the migration and accumulation of docosahexaenoic acid (DHA). Phosphocholine cytidylyltransferase (CCT), a key enzyme involved in PC synthesis, profoundly impacts lipid metabolism in plants; however, few studies have focused on CCT in microorganisms. We investigated the effects of CCT overexpression on lipid metabolism in Schizochytrium sp. CCT overexpression slightly inhibited cell growth, but significantly promoted total lipid synthesis. Compared to the wild-type strain, PUFA content and DHA production in the CCT-overexpressing strain (SR21-CCT) increased by about 49% and 46%, respectively. Analysis of phospholipids and quantitative real-time PCR revealed that CCT overexpression enhanced phospholipid synthesis, especially by strengthening glycerophosphorylcholine acylation and de novo PC synthesis pathways, which promote DHA esterification to PC and DHA accumulation in triacylglycerols. This study helps decipher the mechanism correlating phospholipid metabolism and DHA production.