title: Two circadian timing circuits in Neurospora crassa cells share components and regulate distinct rhythmic processes.
abstract: In Neurospora crassa, FRQ, WC-1, and WC-2 proteins comprise the core circadian FRQ-based oscillator that is directly responsive to light and drives daily rhythms in spore development and gene expression. However, physiological and biochemical studies have demonstrated the existence of additional oscillators in the cell that function in the absence of FRQ (collectively termed FRQ-less oscillators [FLOs]). Whether or not these represent temperature-compensated, entrainable circadian oscillators is not known. The authors previously identified an evening-peaking gene, W06H2 (now called clock-controlled gene 16 [ccg-16]), which is expressed with a robust daily rhythm in cells that lack FRQ protein, suggesting that ccg-16 is regulated by a FLO. In this study, the authors provide evidence that the FLO driving ccg-16 rhythmicity is a circadian oscillator. They find that ccg-16 rhythms are generated by a temperature-responsive, temperature-compensated circadian FLO that, similar to the FRQ-based oscillator, requires functional WC-1 and WC-2 proteins for activity. They also find that FRQ is not essential for rhythmic WC-1 protein levels, raising the possibility that this WCFLO is involved in the generation of WC-1 rhythms. The results are consistent with the presence of 2 circadian oscillators within Neurospora cells, which the authors speculate may interact with each other through the shared WC proteins.
authors.affiliation: Department of Biology, Center for Research on Biological Clocks, Texas A&M University, College Station, TX 77843, USA.
authors.forename: Renato M
authors.initials: RM
authors.lastname: de Paula
authors.forename: Zachary A
authors.initials: ZA
authors.lastname: Lewis
authors.forename: Andrew V
authors.initials: AV
authors.lastname: Greene
authors.forename: Kyung Suk
authors.initials: KS
authors.lastname: Seo
authors.forename: Louis W
authors.initials: LW
authors.lastname: Morgan
authors.forename: Michael W
authors.initials: MW
authors.lastname: Vitalini
authors.forename: Lindsay
authors.initials: L
authors.lastname: Bennett
authors.forename: Richard H
authors.initials: RH
authors.lastname: Gomer
authors.forename: Deborah
authors.initials: D
authors.lastname: Bell-Pedersen
mesh_terms: D001683:Biological Clocks / Q000502:physiology*; D002940:Circadian Rhythm / Q000502:physiology*; D004268:DNA-Binding Proteins / Q000502:physiology; D005656:Fungal Proteins / Q000502:physiology*; D009492:Neurospora crassa / Q000502:physiology*; D013696:Temperature; D014157:Transcription Factors / Q000502:physiology
chemical_list: D004268:DNA-Binding Proteins; C087405:FRQ protein, Neurospora crassa; D005656:Fungal Proteins; D014157:Transcription Factors; C105589:wc-1 protein, Neurospora crassa; C103772:white collar 2 protein, Neurospora