A GENE SUPPRESSING THE ALLELIC PROTOPLASMIC INCOMPATIBILITY SPECIFIED BY GENES AT 5 DIFFERENT LOCI IN PODOSPORA-ANSERINA

Protoplasmic incompatibility (PI) in fungi is a phenomenon of immediate cell destruction resulting from the fusion of cells of unlike genotypes. In Podospora anserina, five loci contain genes determining PI as the result of allelic gene interactions. The present work shows that mutations of a gene called modD inhibit allelic PI irrespective of the locus responsible for the phenomenon. Other modD mutations show differential actions on the allelic interactions and on the expression of the two allelic incompatibility genes of the same locus. These results thus suggest that the modD gene product is involved in the trigger mechanism of allelic PI. The modD gene acts in differentiation: it has been previously shown to control proteolytic activities required for exit from stationary phase. There is thus a connection between this function and allelic PI. This leads to the suggestion that allelic incompatibility genes are involved in the control of stationary phase exit to promote differentiation.