Fatty acid desaturases, especially Delta 12 fatty acid desaturases, are key enzymes for the production of unsaturated fatty acids in oleaginous yeasts. In this study, we identified and characterized a gene encoding Delta 12 fatty acid desaturase of Pseudozyma antarctica named PaFAD2. Almost all oleic acid (C18:1) was converted to linoleic acid by the heterologous expression of the PaFAD2 gene in Saccharomyces cerevisiae and Lipomyces starkeyi oleaginous yeast. Notably, PaFad2 converted not only oleic acid to linoleic acid, but also palmitoleic acid (C16:1) to 9,12-hexadecadienoic acid (C16:2). These results indicated that the PaFAD2 gene was very useful for the production of polyunsaturated fatty acids in yeast, including oleaginous yeast. (C) The Society for Biotechnology, Japan. All rights reserved.