Transcriptional repression by glycerol of genes involved in the assimilation of n-alkanes and fatty acids in yeast Yarrowia lipolytica.

The yeast Yarrowia lipolytica assimilates n-alkanes or fatty acids as carbon sources. Transcriptional activation by n-alkanes of ALK1 encoding a cytochrome P450 responsible for the terminal hydroxylation has been well studied so far, but its regulation by other carbon sources is poorly understood. Here, we analyzed the transcriptional regulation of ALK1 by glycerol. Glycerol is a preferable carbon source compared to glucose for Y. lipolytica. The n-decane-induced transcript levels of ALK1 as well as the reporter gene under the control of ALK1 promoter were significantly decreased in the simultaneous presence of glycerol, but not of glucose. Similarly, the expression of PAT1 encoding acetoacetyl-CoA thiolase involved in β-oxidation was induced by n-decane or oleic acid, but its transcript level was decreased when glycerol was supplemented. These results indicate that glycerol represses the transcription of the genes involved in the metabolism of hydrophobic carbon sources in Y. lipolytica. Repression of ALK1 transcription by glycerol was not observed in the deletion mutant of GUT1 encoding glycerol kinase, implying that the phosphorylation of glycerol is required for the glycerol repression.