Light and electron microscope study of unilateral mating between a secondary mutant and a wild-type strain ofSchizophyllum commune

Summary After hyphal fusions between the secondary mutant and wild-type strains ofSchizophyllum commune some of the fused hyphae show several nuclei per cell and dissolved septa. These hyphae are designated migration hyphae because they are evidently the main routes of nuclear exchange between the two strains. On the wild-type side of the mating the nuclei spread gradually from the main part of the migration hyphae into the side branches, which develop into an extensive network with many anastomoses. The first cells with pseudoclamps or clamp connections are observed in this network.On the mutant side of the mating the branching is less developed and the number of anastomoses is smaller. The cross walls of the septa are poorly dissolved, and nuclear aggregations occur in the hyphae. No development of clamp connections or pseudoclamps is observed. It is suggested that the unilateral mating response of the secondary mutant strain might possibly be caused by the failure of the septa in the mutant hyphae to dissolve, which inhibits the distribution of the nuclei into the side branches of migration hyphae.