A genetic selection for circadian output pathway mutations in Neurospora crassa.
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.
Vitalini
Michael W
MW
Center for Biological Clocks Research and Program for the Biology of Filamentous Fungi, Department of Biology, Texas A&M University, College Station, Texas 77843, USA.
Morgan
Louis W
LW
March
Irene J
IJ
Bell-Pedersen
Deborah
D
D015152:Blotting, Northern; D002940:Circadian Rhythm; D003720:Densitometry; D005656:Fungal Proteins / Q000235:genetics; D005786:Gene Expression Regulation; D005821:Genetic Techniques; D005838:Genotype; D008954:Models, Biological; D016297:Mutagenesis, Site-Directed; D009154:Mutation; D009492:Neurospora crassa / Q000235:genetics*; D009696:Nucleic Acids / Q000737:chemistry; D009991:Oscillometry; D010641:Phenotype; D010957:Plasmids / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012313:RNA / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D013997:Time Factors; D014466:Ultraviolet Rays
C087405:FRQ protein, Neurospora crassa; D005656:Fungal Proteins; D009696:Nucleic Acids; D012333:RNA, Messenger; D012313:RNA