Abstract: The ability of certain yeasts to accumulate high amounts of lipids has been known for years,but only in the last decades,real efforts have been made to unravel the underlying biochemical pathways.In this study,an oleaginous yeast strain Rhodosporidium kratochvilovae YM25235 was used to analyze the correlation between its cold adaptation and membrane fluidity,changes in the content of polyunsaturated fatty acids and mRNA expression level of Δ12-desaturase gene.The results showed that YM25235 could grow at 5—35 ℃,with the optimum temperature of 30 ℃.The membrane fluidity of YM25235 cells was significantly reduced when the culture temperature decreased,but the content of polyunsaturated fatty acids (Linoleic acid and α-Linolenic acid) was increased significantly from 24.35% to 40.32%,and the mRNA abundance of Δ12-desaturase gene was 3.4-fold higher in cells grown at 15 ℃ than in cells grown at 30 ℃.These results indicated that reduced membrane fluidity at low temperature induced genes expression of polyunsaturated fatty acids biosynthesis,which caused higher content of polyunsaturated fatty acids accumulating in cells and enhanced the cold adaptation.