Ultrastructure of an indigotin-producing dome mutant of Schizophyllum commune

Electron microscopic observations of an indigotin-producing dome mutant of Schizophyllum commune Fr. have shown that large wall ingrowths occur within the hyphae. These ingrowths are coupled with morphological abnormalities produced by the dome mutation. The pigment indigotin appears to be produced by progressive condensation within vacuoles and to a lesser extent within the wall ingrowths. Cytochemical techniques have shown that the wall ingrowths are similar in structure to the hyphal walls. there was no evidence for the passage of condensed indigotin into the medium; the pigment granules found in the medium must therefore form outside the hyphae.