Regulatory Mechanisms of EPA and DHA Proportions in a PUFA-Producing Microalga, Schizochytrium sp. ATCC 20888: From the Biosynthesis and Storage Distribution Aspects

Schizochytrium sp. ATCC
20888 is
an important species for industrial polyunsaturated fatty acids (PUFA)
production. This study investigated the regulatory mechanisms affecting
the proportions of eicosapentaenoic acid (EPA) and docosahexaenoic
acid (DHA) in terms of biosynthesis and storage distribution. EPA
and DHA possessed different accumulation patterns: EPA proportion
increased over time, while DHA peaked at 48 h. EPA was predominantly
integrated into triacylglycerol during the logarithmic phase and phosphatidylcholine
during the stationary phase. Transcriptome analysis revealed that
EPA synthesis involved the fatty acid synthase–elongase/desaturase
system, while DHA depended mainly on PUFA synthase. Key enzymes, including
elongase ELOVL7, diacylglycerol acyltransferase (g10562), and lysophosphatidylcholine
acyltransferases (g8836 and g7540), show a positive correlation with
EPA yield, highlighting their roles in its biosynthesis and storage.
Additionally, phosphopantetheine adenylyl transferase (PPAT/COASY)
and ADP-ribosylation factor 1_2 (ARF1_2) were identified as potential
regulators of PUFA proportions. This study provided insights for genetic
optimization of PUFA production inSchizochytrium.