Genomic and transcriptomic analysis screening key genes for (+)-valencene biotransformation to (+)-nootkatone in Yarrowia lipolytica.

Yarrowia lipolytica is a kind of unconventional yeast, which is widely used in food industry because of its safety. (+)-Nootkatone, the ketone derivatives of (+)-valencene, possesses typical grapefruit aroma and is used as aromatics and medicines. It was found that Yarrowia lipolytica was an efficient biocatalyst for the transformation of (+)-valencene to (+)-nootkatone. Thus, it was meaningful to explore the genome features and the gene expression differences of strain Yarrowia lipolytica during (+)-valencene biotransformation, and to study the detailed bioconversion pathways. The results showed that the Yarrowia lipolytica genome was about 20.49 Mb, which encoded 6 137 protein coding genes. There were 1 167 differentially expressed genes (DEGs) in Y_V_36h ((+)-valencene-treated condition) compared to Y_36h ((+)-valencene-untreated blank). During biotransformation, the expression of genes related to the biosynthesis of secondary metabolites and most of ATP-binding cassette (ABC) transporters were significantly up-regulated. In addition, the expression of genes involved in energy metabolism decreased. Moreover, the enzymes participated in (+)-valencene biotransformation were inducible and they were inhibited by cytochrome P450 inhibitors. Several differentially expressed genes related to cytochrome P450 and dehydrogenase (gene2800, gene2911 and gene3152) were significantly up-regulated and might be responsible for converting (+)-valencene to (+)-nootkatone. The RT-qPCR experiment of ten DEGs were further verified and confirmed the reliability of transcriptome results. This study provided a basis for exploring the related genes and molecular regulatory mechanism of (+)-nootkatone biosynthesis from (+)-valencene by Yarrowia lipolytica.