Functional identification and regulatory analysis of Δ(6)-fatty acid desaturase from the oleaginous fungus Mucor sp. EIM-10.

OBJECTIVES: To enlarge the diversity of the desaturases associated with PUFA biosynthesis and to better understand the transcriptional regulation of desaturases, a Δ(6)-desaturase gene (Md6) from Mucor sp. and its 5'-upstream sequence was functionally identified in Saccharomyces cerevisiae.

RESULTS: Expression of the Δ(6)-fatty acid desaturase (Md6) in S. cerevisiae showed that Md6 could convert linolenic acid to γ-linolenic acid. Computational analysis of the promoter of Md6 suggested it contains several eukaryotic fundamental transcription regulatory elements. In vivo functional analysis of the promoter showed the 5'-upstream sequence of Md6 could initiate expression of GFP and Md6 itself in S. cerevisiae. A series deletion analysis of the promoter suggested that sequence between -919 to -784 bp (relative to start site) named as eMd6 is the key factor for high activity of Δ(6)-desaturase. The activity of Δ(6)-desaturase was increased by 2.8-fold and 2.5-fold when the eMd6 sequence was placed upstream of -434 with forward or reverse orientations respectively.

CONCLUSION: To our best knowledge, the native promoter of Md6 from Mucor is the strongest promoter for Δ(6)-desaturase reported so far and the sequence between -919 to -784 bp is an enhancer for Δ(6)-desaturase activity.