genetic selection for circadian output pathway mutations in Neurospora crassa

• Published in: Genetics (Austin) 2004-05, Vol.167 (1), p.119-129
• Main Authors: Vitalini, M.W, Morgan, L.W, March, I.J, Bell-Pedersen, D
• Format: Article
• Language: English
• Subjects: Blotting, Northern; Circadian Rhythm; Densitometry; Fungal Proteins - genetics; Fungi; Gene expression; Gene Expression Regulation; Genes; Genetic Techniques; Genetics; Genotype; Models, Biological; Mutagenesis, Site-Directed; Mutation; Neurospora crassa; Neurospora crassa - genetics; Nucleic Acids - chemistry; Oscillometry; Phenotype; Plasmids - metabolism; Promoter Regions, Genetic; RNA - metabolism; RNA, Messenger - metabolism; Time Factors; Ultraviolet Rays
• ISSN: 0016-6731; 1943-2631; 1943-2631
• DOI: 10.1534/genetics.167.1.119

In most organisms, circadian oscillators regulate the daily rhythmic expression of clock-controlled genes (ccgs). However, little is known about the pathways between the circadian oscillator(s) and the ccgs. In Neurospora crassa, the frq, wc-1, and wc-2 genes encode components of the frq-oscillator. A functional frq-oscillator is required for rhythmic expression of the morning-specific ccg-1 and ccg-2 genes. In frq-null or wc-1 mutant strains, ccg-1 mRNA levels fluctuate near peak levels over the course of the day, whereas ccg-2 mRNA remains at trough levels. The simplest model that fits the above observations is that the frq-oscillator regulates a repressor of ccg-1 and an activator of ccg-2. We utilized a genetic selection for mutations that affect the regulation of ccg-1 and ccg-2 by the frq-oscillator. We find that there is at least one mutant strain, COP1-1 (circadian output pathway derived from ccg-1), that has altered expression of ccg-1 mRNA, but normal ccg-2 expression levels. However, the clock does not appear to simply regulate a repressor of ccg-1 and an activator of ccg-2 in two independent pathways, since in our selection we identified three mutant strains, COP1-2, COP1-3, and COP1-4, in which a single mutation in each strain affects the expression levels and rhythmicity of both ccg-1 and ccg-2.