Phospholipid synthesis pathways in S. cerevisiae. The pathways shown for the synthesis of phospholipids include the relevant steps discussed in this review. The genes that are known to encode enzymes catalyzing individual steps in the lipid synthesis pathways are indicated. The UASINO-containing genes that are subject to regulation by the Ino2p-Ino4p activator complex and the Opi1p repressor are shown (blue). Abbreviations: CDP-DAG, CDP-diacylglycerol; Cho, choline; CL, cardiolipin; Gro, glycerol; DHAP, dihydroxyacetone phosphate; Etn, ethanolamine; Glc, glucose; Ins, inositol; PA, phosphatidate; PC, phosphatidylcholine; PE, phosphatidylethanolamine; PG, phosphatidylglycerol; PGP, phosphatidylglycerophosphate; PDE, phosphatidyldimethylethanolamine; PI, phosphatidylinositol; PME, phosphatidylmonomethylethanolamine; PS, phosphatidylserine; TAG, triacylglycerol; UASINO, an inositol-responsive upstream activating sequence.