Differential DNA methylation during the vegetative life cycle of Neurospora crassa.

Isotope dilution gas chromatography-mass spectrometry analysis of genomic DNAs isolated from the different growth phases of Neurospora crassa revealed significant differences in the amounts of 5-methylcytosine; the mol % of 5-methylcytosine was 0.36 in conidia (asexual spores), 0.40 in conidial germlings cultured for 3 h, 0.24 in mycelial cells that had grown exponentially for 6 and 12 h, and 0.40 in stationary-phase mycelial cells. These results indicate an approximate inverse correlation between the level of C methylation in the DNA and the presumed level of developmentally related transcriptional activity.