RESUMEN
Sterol 14α-demethylase catalyzes lanosterol hydroxylation, which is one of the key reactions in the biosynthetic pathway of sterols. There is only one sterol 14α-demethylases gene named Erg11 in Saccharomyces cerevisiae genome. In this study, three sterol 14α-demethylases genes named AoErg11A, AoErg11B and AoErg11C were identified in Aspergillus oryzae genome through bioinformatics analysis. The function of these three genes were studied by yeast complementation, and the expression pattern/subcellular localization of these genes/proteins were detected. The results showed that the three AoErg11s were expressed differently at different growth times and under different abiotic stresses. All of the three proteins were located in endoplasmic reticulum. The AoErg11s could not restore the temperature-sensitive phenotype of S. cerevisiae erg11 mutant. Overexpression of the three AoErg11s affected both growth and sporulation, which may be due to the effect of AoErg11s on ergosterol content. Therefore, this study revealed the functions of three AoErg11s and their effects on the growth and ergosterol biosynthesis of A. oryzae, which may contribute to the further understanding of the ergosterol biosynthesis and regulation mechanism in this important filamentous fungus, A. oryzae.
RESUMEN
Thiolase plays important roles in lipid metabolism. It can be divided into degradative thiolases (thioase I) and biosynthetic thiolases (thiolases II), which are involved in fatty acid ß-oxidation and acetoacetyl-CoA biosynthesis, respectively. The Saccharomyces cerevisiae genome harbors only one gene each for thioase I and thiolase II, namely, Pot1 and Erg10, respectively. In this study, six thiolases (named AoErg10A to AoErg10F) were identified in Aspergillus oryzae genome using bioinformatics analysis. Quantitative reverse transcription-PCR (qRT-PCR) indicated that the expression of these six thiolases varied at different growth times and under different forms of abiotic stress. Subcellular localization analysis showed that AoErg10A was located in the cytoplasm, AoErg10B and AoErg10C were in the mitochondria, and AoErg10D, AoErg10E, and AoErg10F were in the peroxisome. Yeast heterologous complementation assays revealed that AoErg10A, AoErg10D, AoErg10E, AoErg10F, and cytoplasmic AoErg10B (AoErg10BΔMTS) recovered the phenotypes of S. cerevisiae erg10 weak and lethal mutants and that only AoErg10D, AoErg10E, and AoErg10F recovered the phenotype of the pot1 mutant that cannot use oleic acid as the carbon source. Overexpression of AoErg10s affected either the growth speed or the sporulation of the transgenic strains. In addition, the fatty acid and ergosterol content changed in all the AoErg10-overexpressing strains. This study revealed the function of six thiolases in A. oryzae and their effect on growth and fatty acid and ergosterol biosynthesis, which may lay the foundation for genetic engineering for lipid metabolism in A. oryzae or other fungi. IMPORTANCE Thiolases, including thioase I and thiolase II, play important roles in lipid metabolism. Aspergillus oryzae, one of the most industrially important filamentous fungi, has been widely used for manufacturing oriental fermented food such as sauce, miso, and sake for a long time. In addition, A. oryzae has a high capability in production of high lipid content and has been used for lipid production. Thus, it is very important to investigate the function of thiolases in A. oryzae. In this study, six thiolase (named AoErg10A to AoErg10F) were identified by bioinformatics analysis. Unlike other reported thiolases in fungi, three of the six thiolases showed dual functions of thioase I and thiolase II in S. cerevisiae, indicating that the lipid metabolism is more complex in A. oryzae. The reveal of function of these thiolases in A. oryzae can lay the foundation for genetic engineering for lipid metabolism in A. oryzae or other fungi.
