HOMOLOGY-DEPENDENT SILENCING OF THE SC3 GENE IN SCHIZOPHYLLUM-COMMUNE

After introduction of extra copies of the SC3 hydrophobin gene into a wild-type strain of Schizophyllum commune, gene silencing was observed acting on both endogenous and introduced SC3 genes in primary vegetat ive transformants. Nuclear run-on experiments indicated that silencing acted at the transcriptional level. Southern analysis revealed that c ytosine methylation of genomic DNA occurred. Moreover, SC3 silencing w as suppressed by exposure to 5-azacytidine during growth. After growth of SC3-suppressed colonies from homogenized mycelium or from colonies stored at 4 degrees, SC3 transcription was restored. However, after p rolonged growth SC3 silencing was again observed. Introduction of a pr omoterless SC3 fragment into wild type gave less SC3 silencing.