Differences between hybridizable RNA during growth and differentiation of Physarum polycephalum

The differences between hybridizable RNA during growth and during differentiation (spherulation) of the slime mold Physarum polycephalum were studied. Two modified methods were used for characterization of the classes of hybridizable RNA, according to their mobility on polyacrylamide gels. It was found that some heavier classes of RNA were depressed or quantitatively diluted during spherulation, compared with growth, whereas new classes are synthesized during the process. Most of the new classes have s-values lower than 10 S. These findings confirm the suggestions previously made that some classes of RNA are depressed during spherulation, whereas new classes are synthesized. This is consistent with the idea about the importance of transcription in differentiation.