Isolation and transformation of uracil auxotrophs of the lignin-degrading basidiomycete Phanerochaete chrysosporium.

Uracil auxotrophs of Phanerochaete chrysosporium were isolated using 5-fluoroorotate resistance as a selection scheme. The ura3 auxotrophs deficient in orotidylate decarboxylase and ura5 auxotrophs deficient in orotate phosphoribosyl transferase were characterized by enzyme assays and complementation tests. The ura5 auxotrophs were transformed to prototrophy with the ura5 gene from the ascomycete Podospora anserina. The ura3 auxotrophs were transformed to prototrophy with the ura3 gene from the basidiomycete Schizophyllum commune. The P. chrysosporium ura3 gene was isolated from a lambda EMBL3 genomic library using the S. commune ura3 gene as a probe. A 6.6-kb fragment incorporating the ura3 gene was subcloned into Bluescript SK+(pURA3.1) and used to transform P. chrysosporium ura3 auxotrophic strains. The pURA3.1 insert was mapped for restriction sites and the approximate location of the ura3 gene within the insert was determined. Double auxotrophic strains were transformed with either of two marker genes and the resulting single auxotrophic strains were crossed to demonstrate genetic recombination between two nuclei of identical genetic background.