Nuclear division cycle in germinating conidia of Neurospora crassa.

A temperature-sensitive mutant has been shown to be blocked at a specific point in the nuclear division cycle: just before the initiation of DNA synthesis at the time when the spindle pole bodies have duplicated but not separated. The metabolic activities of conidia of this mutant strain at the nonpermissive temperature have led us to conclude that the nuclei in a population of dormant conidia are arrested at various points in the nuclear division cycle. This conclusion is substantiated by the activities of conidia in the presence of the inhibitory drugs cycloheximide and hydroxyurea. In each inhibitory situation we observed that some, but not all, of the conidia were able to accomplish DNA synthesis and/or nuclear division.