Role of g 6 pdh and leuB on Lipid Accumulation in Mucor circinelloides .

Mucor circinelloides is a valuable oleaginous filamentous fungus rich in γ-linolenic acid (GLA, 18:3; n-6), which is beneficial for human health. Our previous comparative proteomic analysis between high lipid-producing M. circinelloides WJ11 and low lipid-producing M. circinelloides CBS 277.49 indicated that glucose 6-phosphate dehydrogenase (G6PDH) and β-isopropylmalate dehydrogenase (IPMDH) were closely involved in lipid accumulation. Transcription analysis suggested that in the strain WJ11, g 6 pdh 1 and g 6 pdh 2, which encode G6PDH, and leuB , which encodes IPMDH, could be the key genes regulating lipid accumulation. To further analyze the effects of these three genes (i.e., g 6 pdh 1, g 6 pdh 2, and leuB ) on lipid accumulation, we respectively overexpressed these genes from M. circinelloides WJ11 in defective CBS 277.49 strains in this study. The results showed that overexpression of g 6 pdh 1 and g 6 pdh 2 genes from strain WJ11 increased the fatty acid content of cell dry weight by 23-38 and 41-47%, respectively, compared with the control strain. Furthermore, overexpression of the leuB gene from strain WJ11 increased the fatty acid content of cell dry weight by up to 67-73%. These results suggest that g 6 pdh 1, g 6 pdh 2, and especially leuB genes play important roles in regulating fatty acid synthesis in M. circinelloides .