Absence of differences in polysomal RNAs from vegetative monokaryotic and dikaryotic cells of the fungus Schizophyllum commune

Total polysomes, including free and membrane-bound polysomes, were isolated from the monokaryotic and dikaryotic mycelial cell types of the basidiomycete Schizophyllum commune grown under submerged conditions. Sucrose gradient centrifugation showed that these isolated polysomes had a size distribution as expected for polysomes functioning in vivo and thus contained intact mRNA. RNA preparations extracted from the polysomes were used to analyze the mRNA sets in the monokaryon and dikaryon. Saturation hybridization of single-copy DNA with a vast excess of polysomal RNA and cell-free translation of polysomal RNA in a wheat germ system followed by two-dimensional gel electrophoresis of the products did not reveal significant differences between the mRNA sets in both mycelial cell types. Moreover, it was found that the sequence complexities and coding properties of polysomal RNA and total (nuclear and cytoplasmic) RNA from S. commune are not detectably different. From these results and those obtained in previous studies it was concluded that the differentiation between monokaryotic and dikaryotic mycelial cell types as controlled by A and B incompatibility genes involves differential modification of polypeptides during or after mRNA translation.