Developmental regulation of the methylation of the ribosomal DNA in the basidiomycete fungusSchizophyllum commune

Summary We started partial overlapping hybridization on chromosome V from the centromere-linked gene SU8 towards centromere 5. Transformation of Podospora anserina with the cloned sequences and subsequent genetic analysis reveal that cosmids issuing from a 60 kb region never integrate near centromere 5, whereas cosmids from either side return mostly to this locus. Molecular analysis shows that heterologous integrations of cosmids spanning the 60 kb region occurs in a specific sequence of 11 kb common to all the inserts. We propose that this sequence contains a gene or a structure which is lethal in a duplicated form. Straightforward interpretation of genetic data suggests that this structure does not correspond to centromere 5. Its function is still unknown.