Abstract: Δ12-desaturase is a key enzyme in the biosynthesisi of polyunsaturated fatty acid.In this study,based on the sequence information of the known yeast Δ12-desaturase genes,a pair of specific primers was designed and used for the amplification of Rhodosporidium kratochvilovae YM25235 Δ12-desaturase gene.A full-length coding sequence of 1341bp was amplified.Sequence analysis showed that the sequence contained a complete open reading frame encoding a protein of 446 amino acids with a molecular weight of 50.6ku.The deduced amino acid sequence showed the highest similarity to the known Δ12-desaturases that characteristic of three conserved histidine-rich region,indicating that the cDNA sequence is a new Δ12-desaturase gene.In order to verify its function,the coding sequence was further subcloned into expression vector pYES3/CT.Recombinant plasmid pY3RKD12 was constructed and then transformed into Saccharomyces cerevisiae strain INVScl for heterologous express.Total fatty acid analysis by gas chromatography (GC) showed that a novel peak corresponding to the standards of linoleic acid methyl ester was detected with the same retention time in pY3RKD12-tranformed yeast cells,which was absent in the cell transformed with pYES3/CT.The ratio of this new fatty acid to total fatty acids was 3.76%.All these results demonstrated that the cloned sequence whose coding product exhibited Δ12-fatty acid desaturase activity to convert oleic acid to linoleic acid is a novel Δ12-fatty acid desaturase gene.