title: A new mutation affecting FRQ-less rhythms in the circadian system of Neurospora crassa.
abstract: We are using the fungus Neurospora crassa as a model organism to study the circadian system of eukaryotes. Although the FRQ/WCC feedback loop is said to be central to the circadian system in Neurospora, rhythms can still be seen under many conditions in FRQ-less (frq knockout) strains. To try to identify components of the FRQ-less oscillator (FLO), we carried out a mutagenesis screen in a FRQ-less strain and selected colonies with altered conidiation (spore-formation) rhythms. A mutation we named UV90 affects rhythmicity in both FRQ-less and FRQ-sufficient strains. The UV90 mutation affects FRQ-less rhythms in two conditions: the free-running long-period rhythm in choline-depleted chol-1 strains becomes arrhythmic, and the heat-entrained rhythm in the frq(10) knockout is severely altered. In a FRQ-sufficient background, the UV90 mutation causes damping of the free-running conidiation rhythm, reduction of the amplitude of the FRQ protein rhythm, and increased phase-resetting responses to both light and heat pulses, consistent with a decreased amplitude of the circadian oscillator. The UV90 mutation also has small but significant effects on the period of the conidiation rhythm and on growth rate. The wild-type UV90 gene product appears to be required for a functional FLO and for sustained, high-amplitude rhythms in FRQ-sufficient conditions. The UV90 gene product may therefore be a good candidate for a component of the FRQ-less oscillator. These results support a model of the Neurospora circadian system in which the FRQ/WCC feedback loop mutually interacts with a single FLO in an integrated circadian system.
authors: Department of Biology, York University, Toronto, Canada.
authors: Sanshu
authors: S
authors: Li
authors: Kamyar
authors: K
authors: Motavaze
authors: Elizabeth
authors: E
authors: Kafes
authors: Sujiththa
authors: S
authors: Suntharalingam
authors: Patricia
authors: P
authors: Lakin-Thomas
mesh_terms: D000483:Alleles; D001683:Biological Clocks; D002794:Choline / Q000378:metabolism; D002940:Circadian Rhythm; D003433:Crosses, Genetic; D003470:Culture Media; D005656:Fungal Proteins / Q000235:genetics* / Q000378:metabolism; D015966:Gene Expression Regulation, Fungal; D055785:Gene Knockdown Techniques; D005838:Genotype; D006358:Hot Temperature; D016254:Mutagenesis, Insertional / Q000379:methods; D009154:Mutation; D009492:Neurospora crassa / Q000235:genetics* / Q000254:growth & development / Q000502:physiology; D010641:Phenotype; D013172:Spores, Fungal / Q000235:genetics / Q000254:growth & development / Q000528:radiation effects; D014466:Ultraviolet Rays
chemical_list: D003470:Culture Media; C087405:FRQ protein, Neurospora crassa; D005656:Fungal Proteins; D002794:Choline