A HOMOLOGOUS GENE-REPORTER SYSTEM FOR THE BASIDIOMYCETE SCHIZOPHYLLUM-COMMUNE BASED ON INTERNALLY DELETED HOMOLOGOUS GENES

Problems encountered in our attempts to achieve expression of heterolo gous genes, driven by ascomycetous regulatory sequences, in homobasidi omycetes led us to develop a gene-reporter system based on the express ion of homologous genes in Schizophyllum commune. Internal deletions w ere made in the coding sequences of the regulated Sc4 gene and the con stitutively expressed GPD gene. After introduction of these constructs into S. commune it was found that the expected truncated transcripts were produced. The internally deleted Sc4 gene, containing 1140 bp of upstream and 200 bp of downstream sequences, was only expressed in dik aryons at the time of fruiting (as was the resident Sc4 gene) but not at all in monokaryons, indicating that the construct contained all reg ulatory sequences necessary and sufficient to confer control by the ma ting-type genes and expression during fruiting. The internally deleted GPD gene, containing 1300 bp of upstream and 150 bp of downstream seq uences, was expressed both in monokaryons and dikaryons at levels simi lar to those of the resident GPD gene, indicating that all sequences n ecessary for proper expression were present. This reporter-gene system may be applicable to the analysis of cis-regulatory sequences of thes e genes. Furthermore, heterologous genes may be inserted into the well -expressed GPD deletion construct to obtain expression of such genes i n S. commune and possibly in other homobasidiomycetes.