Homologous expression of recombinant manganese peroxidase genes in ligninolytic fungus Pleurotus ostreatus

Pleurotus ostreatus is a white-rot fungus known as an efficient degrader of lignin and also various organo-pollutants. Using a DNA-mediated transforma tion system, a molecular breeding approach to isolate overproducers of a ma nganese peroxidase isozyme, MnP3, was carried out. Recombinant mnp3 constru cts under the control of P. ostreatus us sdi1 expression signals were intro duced into the wild-type P. ostreatus strain by co-transformation with a ca rboxin-resistant vector plasmid, pTM1. One of the recombinants obtained by a mating between two monokaryotic transformants, TMG9-C1, showed a several. times higher level of MnP activity than the wild-type control in the early stage of liquid culture. Predominant transcription of the recombinant mnp3 in the strain was demonstrated by RT-PCR experiments. This is the first re port of a genetically modified P. ostreatus strain with an expression syste m for recombinant genes.