POLYUNSATURATED FATTY-ACID BIOSYNTHESIS IN SACCHAROMYCES-CEREVISIAE -EXPRESSION OF ETHANOL TOLERANCE AND THE FAD2 GENE FROM ARABIDOPSIS-THALIANA

The Arabidopsis thaliana Delta-12 fatty acid desaturase gene (FAD2) wa s overexpressed in Saccharomyces cerevisiae by using the GAL1 promoter , S. cerevisiae harboring the FAD2 gene was capable of forming hexadec adienoyl (16:2) and linoleoyl (18:2) residues in the membrane lipid wh en cultured in medium containing galactose. Gas-liquid chromatography analysis of total lipids indicated that the transformed S. cerevisiae accumulated these dienoic fatty acyl residues and that they accounted for approximately 50% of the total fatty acyl residues. Phospholipid a nalysis of this strain indicated that the oleoyl (18:1) residue bindin g phosphatidylcholine (PC) was mostly converted to the 18:2 residue bi nding PC, whereas 50% of the palmitoleoyl (16:1) residue binding PC wa s converted to the 16:2 residue binding PC. A marked effect on the uns aturation of 16:1 and 18:1 was observed when S. cerevisiae harboring t he FAD2 gene was cultured at 8 degrees C. To assess the ethanol tolera nce of S. cerevisiae producing polyunsaturated fatty acids, the cell v iability of this strain in the presence of ethanol was examined. The r esults indicated that S. cerevisiae cells overexpressing the FAD2 gene had greater resistance to 15% (vol/vol) ethanol than did the control cells.