Isolation and transformation of uracil auxotrophs of the edible basidiomycete Pleurotus ostreatus

Uracil auxotrophs of Pleurotus ostreatus were isolated using the selectable marker, resistance to 5′-fluoro-orotic acid (5′-FOA). Two of the nine uracil auxotrophs obtained were transformed to prototrophy using plasmid pTRura 3-2 that contains the orotidine monophosphate decarboxylase ( ura3) gene from Trichoderma reesei. Southern blot analyses of the transformants showed that the transforming DNA had integrated into the genome of the protoplasts. Using 2×10 7 protoplasts, this system gave a transformation efficiency of about 30 transformants per μg of DNA. Normal fruiting bodies were induced in the transformants by crossing them with wild-type monokaryons, and the basidiospores collected from these fruiting bodies showed a biased segregation rate to prototrophy. These results indicate the integrated DNA was stably inherited.