Acyltransferases are provided, suitable for use in the manufacture of microbial oils enriched in omega fatty acids in oleaginous yeast (e.g., Yarrowia lipolytica). Specifically, genes encoding diacylglycerol acyltransferase (DGAT1) have been isolated from Y. lipolytica and Mortierella alpina. These genes encode enzymes that participate in the terminal step in oil biosynthesis in yeast. Each is expected to play a key role in altering the quantity of polyunsaturated fatty acids produced in oils of oleaginous yeasts.