Genome analysis of filamentous fungi:: identification and characterization of an unusual GT-rich minisatellite in the ascomycete Podospora anserina

A genomic DNA fragment, PaGT7-5, of Podospora anserina was cloned that contains three different repetitive sequence motifs including a minisatellite with an unusual structure. This element, PaMin1, consists of ten copies of a 16 bp repeat unit with five GT dinucleotide repeats. Adjacent to PaMin1, a short poly(GT) stretch and four repeats of a 12 bp sequence were identified. Six alleles which differ in the number of the minisatellite unit were demonstrated in 18 different P. anserina strains. The flanking sequences of PaMin1 did not display any sequence alterations. A PCR analysis of total DNA from cultures of different age revealed no sequence changes, indicating that this repetitive DNA remains stable during aging. Southern-blot hybridization experiments of DNA from different strains detected only minor fragment length polymorphisms in the immediate vicinity of PaMin1. In contrast, maj or polymorphisms were observed at a greater distance from the locus indicating that this locus can be used as an informative probe to discriminate between different P. anserina strains.