Study on the regulatory effects of Δ4-DES and LACS genes on the synthesis of LC-PUFAs, based on the transcriptome changes induced by fluridone in Aurantiochytrium limacinum OUC86.

In this study, fluridone was utilized to induce Aurantiochytrium limacinum OUC86 to identify the key genes involved in the synthesis of Long-chain Polyunsaturated Fatty Acids (LC-PUFAs). With the increase of fluridone concentration, the lipid content increased, the proportion of EPA was the highest under the treatment of 75 mg/L fluridone ethanol solution. Transcriptome sequencing analysis of A. limacinum was conducted, and differential expression genes related to fatty acid metabolism were identified. The transcript levels of Δ4 desaturase gene (Δ4-DES) and long-chain acyl-coenzyme A synthetase gene (LACS) showed significant changes, with KEGG metabolic pathway analysis indicating their crucial roles in the conversion of LC-PUFAs, potentially closely related to the increase in EPA and DHA content. Therefore, these two genes were recombinant expressed in Saccharomyces cerevisiae to study their functions. Compared to the untransformed yeast strain YS-Δura3, the recombinant strains YS-Δ4 and YS-LACS exhibited an increase in the proportion of LC-PUFAs. The lipid content in YS-Δ4 increased by 18.82%, while DPA content decreased by 67.02%, and DHA content increased by 115.85% at 48 h. In YS-LACS, EPA content increased by 132.86%, DPA content rose by 62.65%, and DHA content increased by 33.33% at 24 h. These results suggest that the expression of Δ4-DES can promote the synthesis of long-chain fatty acids and significantly facilitate the conversion of DPA to DHA; and the expression of LACS significantly promotes the synthesis of EPA, DPA, and DHA, which provide potential genetic targets for regulating the fatty acid composition of A. limacinum through genetic engineering.