Resistance to imidazoles and triazoles in Saccharomyces cerevisiae as a new dominant marker.

The imidazole and triazole fungicides inhibit cytochrome P450 14 alpha-lanosterol demethylase (P45014DM) implicated in the ergosterol biosynthesis pathway, which is specific to fungi and yeasts. Two plasmids were obtained which allow triazole and imidazole resistance in Saccharomyces cerevisiae. The low copy number plasmid (pFD 383) encodes cytochrome P450 C14 alpha lanosterol demethylase under the control of phospho-glycerate-kinase promoter. S. cerevisiae transformed by the pFD 383 plasmid are resistant to imidazoles and triazoles. Moreover, this transformed strain shows increased levels of P45014DM mRNA and of cytochrome P450. A second low copy number plasmid (pFD 384) carries a mutant cytochrome P450 14 alpha lanosterol demethylase gene, which increases imidazole and triazole resistance. These constructions can be used on a dominant selection marker to transform wild-type yeasts and to confer imidazole and triazole resistance in industrial fermentation.