A HAD family phosphatase CSP-6 regulates the circadian output pathway in Neurospora crassa

PLoS Genet. 2018 Jan 19;14(1):e1007192. doi: 10.1371/journal.pgen.1007192. eCollection 2018 Jan.


Circadian clocks are ubiquitous in eukaryotic organisms where they are used to anticipate regularly occurring diurnal and seasonal environmental changes. Nevertheless, little is known regarding pathways connecting the core clock to its output pathways. Here, we report that the HAD family phosphatase CSP-6 is required for overt circadian clock output but not for the core oscillation. The loss of function Δcsp-6 deletion mutant is overtly arrhythmic on race tubes under free running conditions; however, reporter assays confirm that the FREQUENCY-WHITE COLLAR COMPLEX core circadian oscillator is functional, indicating a discrete block between oscillator and output. CSP-6 physically interacts with WHI-2, Δwhi-2 mutant phenotypes resemble Δcsp-6, and the CSP-6/WHI-2 complex physically interacts with WC-1, all suggesting that WC-1 is a direct target for CSP-6/WHI-2-mediated dephosphorylation and consistent with observed WC-1 hyperphosphorylation in Δcsp-6. To identify the source of the block to output, known clock-controlled transcription factors were screened for rhythmicity in Δcsp-6, identifying loss of circadian control of ADV-1, a direct target of WC-1, as responsible for the loss of overt rhythmicity. The CSP-6/WHI-2 complex thus participates in the clock output pathway by regulating WC-1 phosphorylation to promote proper transcriptional/translational activation of adv-1/ADV-1; these data establish an unexpected essential role for post-translational modification parallel to circadian transcriptional regulation in the early steps of circadian output.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Circadian Clocks / genetics
  • Circadian Rhythm / genetics*
  • DNA-Binding Proteins / genetics
  • DNA-Binding Proteins / metabolism
  • DNA-Binding Proteins / physiology
  • Fungal Proteins / genetics
  • Fungal Proteins / metabolism
  • Fungal Proteins / physiology*
  • Gene Expression Regulation, Fungal
  • Hydrolases / genetics
  • Hydrolases / physiology*
  • Neurospora crassa / enzymology
  • Neurospora crassa / genetics*
  • Organisms, Genetically Modified
  • Phosphoric Monoester Hydrolases / physiology*
  • Phosphorylation
  • Protein Binding
  • Signal Transduction / genetics
  • Transcription Factors / genetics
  • Transcription Factors / metabolism
  • Transcription Factors / physiology


  • DNA-Binding Proteins
  • Fungal Proteins
  • Transcription Factors
  • wc-1 protein, Neurospora crassa
  • Hydrolases
  • Phosphoric Monoester Hydrolases
  • 2-haloacid dehalogenase