Isolation of the two allelic incompatibility genes s and S of the fungus Podospora anserina

The two allelic genes s and S are responsible for heterogenic incompatibility between wild type strains of the fungus Podospora anserina. The s gene has been cloned by SIB selection and expression in a strain containing a neutral allele of this locus. The S gene was isolated from a genomic library using the DNA of the s locus as a probe. The physical map of the DNA fragments carrying the two genes are highly dissimilar and restriction polymorphism exists at the s locus between s and S strains. Nevertheless, homology between the two alleles was revealed by cross-hybridization at the DNA and RNA levels.