Abstract: Disclosed are microalgal cells having an ablated or downregulated fatty acyl-ACP thioesterase (FATA) gene, wherein the cell is modified to express a heterologous lysophosphatidic acid acyltransferase (LPAAT) comprising an amino acid sequence that has at least 80% identity to an acyltransferase encoded by SEQ ID NO: 90, 89, 92, 93 or 95 and wherein the modified microalgal cell produces an oil with an elevated ratio of saturated-unsaturated-saturated triglycerides over trisaturated triglycerides as compared to a corresponding unmodified cell. Also disclosed are microalgal oils comprising at least 60% stearate-oleate-stearate (SOS) triglycerides, less than 5% trisaturates and wherein the fatty acid profile of the oil comprises at least 50% C18:0. Related methods of producing an oil are also disclosed.

Abstract: Recombinant nucleic acids and vector constructs encoding acyltransferases and variant thioesterases, and the acyltransferases and variant thioesterases encoded by the nucleic acids are provided. The acyltransferases and variant thioesterases are useful in fatty acid synthesis and triacylglycerol production. Host cells that express the recombinant nucleic acids as well as methods of cultivating the host cells, methods of producing oils from the host cells are provided. The recombinant host cells and the oils produced therefrom have altered fatty acid profiles and/or triacylglycerols with altered regiospecificity.