A Genetic Selection for Circadian Output Pathway Mutations in Neurospora crassa

In Neurospora crassa, the frq-oscillator is essential for the rhythmic expression of morning-specific genes, ccg-1 and ccg-2.

• In frq-null or wc-1 mutant strains, ccg-1 mRNA levels fluctuate near peak levels throughout the day, while ccg-2 mRNA remains at trough levels.
• The simplest model suggests that the frq-oscillator regulates a repressor for ccg-1 and an activator for ccg-2.
• A genetic selection identified mutant strain COP1-1, which shows altered expression of ccg-1 mRNA while maintaining normal ccg-2 levels.
• Three additional mutant strains (COP1-2, COP1-3, COP1-4) were found where a single mutation influences both ccg-1 and ccg-2 expression and rhythmicity.

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