Characterization of hch, the Podospora anserina homolog of the het-c heterokaryon incompatibility gene of Neurospora crassa

The het-c. locus controls heterokaryon formation in Neurospora crassa. It i s subject to balancing selection operating to maintain polymorphism at that locus ill natural populations. We have isolated hch, the het-c homolog fro m the related species Podospora anserina (hch for het-c homolog), in order to determine if this gene also functions as a her gene in that species. The hct-e and hch sequences are highly similar but differ in the region defini ng allele: specificity in N. crassa het-c. Analysis of hch variability in 1 1 natural P. anserina isolates with different het genotypes revealed no pol ymorphism. This suggested that hch does not function as a her gene. However , heterologous expression of the N. crassa het-c.(PA) allele in P. anserina triggers a growth defect reminiscent of the het-c incompatibility reaction .