Cross Regulation of Phospholipid and Unsaturated Fatty Acid Biosynthesis

As most cellular phospholipids require unsaturated fatty acids (UFAs), we investigated the potential cross regulation of phospholipid and UFA biosynthesis. The Δ‐9 desaturase, encoded by OLE1 , is the sole source of endogenous UFAs in Saccharomyces cerevisiae . Inspection of the OLE1 promoter revealed several sequences that are close matches to the regulatory sequence UAS INO found in many phospholipid biosynthetic genes, which is the target of regulation by Ino2p, Ino4p and Opi1p. We examined if these proteins also play a role in regulation of OLE1 expression. Reporter gene analysis showed that when uracil prototrophy was placed under control of the OLE1 promoter, poor expression was observed in the opi1 and ino4 mutants. When lacZ was placed under control of the OLE1 promoter, reporter assays confirmed that expression was poor in the tested mutants. qPCR analysis demonstrates that the down regulation of OLE1 occurs normally in opi1, ino2 and ino4 mutants, however, its expression under growth conditions without exogenous UFAs is poor compared to wild type cells. Fatty acid analysis revealed that normal regulation of OLE1 occurred in response to unsaturated fatty acid (UFA) supplement in the opi1 mutant, indicating that post‐transcriptional regulation is still functional. Finally, the 2‐hybrid assay was used to examine potential interactions between Ole1p and Opi1p, Ino2p, Ino4p and known OLE1 regulators Mga2p and Spt23p, however no unexpected interactions were detected. This preliminary work indicates that phospholipid regulators Opi1p, Ino2p, Ino4p play a role in OLE1 expression, but not through regulation in response to UFA supplements or through Mga2p and Spt23p. Support or Funding Information Research reported was supported by the National Institute Of General Medical Sciences of the National Institutes of Health under Award Number R15GM132853