Enhancement of carotenoid production by disrupting the C22-sterol desaturase gene (<it>CYP61</it>) in <it>Xanthophyllomyces dendrorhous</it>

<p>Abstract</p> <p>Background</p> <p><it>Xanthophyllomyces dendrorhous</it> is a basidiomycetous yeast that synthesizes astaxanthin, which is a carotenoid with a great biotechnological impact. The ergosterol and carotenoid synthesis pathways are derived from the mevalonate pathway, and in both pathways, cytochrome P450 enzymes are involved.</p> <p>Results</p> <p>In this study, we isolated and described the <it>X. dendrorhous CYP61</it> gene, which encodes a cytochrome P450 involved in ergosterol biosynthesis. This gene is composed of nine exons and encodes a 526 amino acid polypeptide that shares significant percentages of identity and similitude with the C22-sterol desaturase, CYP61, from other fungi. Mutants derived from different parental strains were obtained by disrupting the <it>CYP61</it> gene with an antibiotic selection marker. These mutants were not able to produce ergosterol and accumulated ergosta-5,8,22-trien-3-ol and ergosta-5,8-dien-3-ol. Interestingly, all of the mutants had a more intense red color phenotype than their respective parental strains. The carotenoid composition was qualitatively and quantitatively analyzed by RP-HPLC, revealing that the carotenoid content was higher in the mutant strains without major changes in their composition. The expression of the <it>HMGR</it> gene, which encodes an enzyme involved in the mevalonate pathway (3-hydroxy-3-methylglutaryl-CoA reductase), was analyzed by RT-qPCR showing that its transcript levels are higher in the <it>CYP61</it> mutants.</p> <p>Conclusions</p> <p>These results suggest that in <it>X. dendrorhous</it>, ergosterol regulates <it>HMGR</it> gene expression by a negative feedback mechanism and in this way; it contributes in the regulation of the carotenoid biosynthesis.</p>