Regulation of proteolytic enzymes in Podospora anserina: selection and properties of self-lysing mutant strains

Abstract

Previous results showed that cell disintegration in the fungus Podospora anserina occured through the action of two proteases, enzymes whose messengers were normally latent during the extension stage of the thallus. We selected three mutant strains in which the constitutive activity of the protease messengers was expressed by an arrest of growth early in development (10 to 30 hours after spore germination) and a reaction of cell disintegration, in the thallus, suppressible with beta-phenyl pyruvic acid, a protease inhibitor. The mutant character is recessive in one strain. In the case of the two strains in which the mutant trait is dominant, reversion studies have revealed that the deregulation resulted from the specific interaction between two genes and we have succeded in creating two non allelic incompatibility systems comparable to the non allelic gene interactions responsible for the incompatibility phenomena found between wild type races. We know, on the whole, that 11 loci are involved in the regulation of the proteases: five were revealed as incompatibility loci and six were discovered from investigations on four self-lysing mutant strains. It is suspected that all these genes act at the post-transcriptionnal level of the synthesis of specific proteolytic enzymes. We propose that the products of two genes act as "repressors" to prevent the protease messengers from being constitutively translated and that the products of the nine remaining genes exert a positive control by inducing translation, at the appropriate time, through the action of effectors resulting from specific interloci cooperation.