Overexpression of White Collar-1 (WC-1) activates circadian clock-associated genes, but is not sufficient to induce most light-regulated gene expression in Neurospora crassa

Mol Microbiol. 2002 Aug;45(4):917-31. doi: 10.1046/j.1365-2958.2002.03074.x.

Abstract

Many processes in fungi are regulated by light, but the molecular mechanisms are not well understood. The White Collar-1 (WC-1) protein is required for all known blue-light responses in Neurospora crassa. In response to light, WC-1 levels increase, and the protein is transiently phosphorylated. To test the hypothesis that the increase in WC-1 levels after light treatment is sufficient to activate light-regulated gene expression, we used microarrays to identify genes that respond to light treatment. We then overexpressed WC-1 in dark-grown tissue and used the microarrays to identify genes regulated by an increase in WC-1 levels. We found that 3% of the genes were responsive to light, whereas 7% of the genes were responsive to WC-1 overexpression in the dark. However, only four out of 22 light-induced genes were also induced by WC-1 overexpression, demonstrating that changes in the levels of WC-1 are not sufficient to activate all light-responsive genes. The WC proteins are also required for circadian rhythms in dark-grown cultures and for light entrainment of the circadian clock, and WC-1 protein levels show a circadian rhythm in the dark. We found that representative samples of the mRNAs induced by over-expression of WC-1 show circadian fluctuations in their levels. These data suggest that WC-1 can mediate both light and circadian responses, with an increase in WC-1 levels affecting circadian clock-responsive gene regulation and other features of WC-1, possibly its phosphorylation, affecting light-responsive gene regulation.

Publication types

  • Research Support, Non-U.S. Gov't
  • Research Support, U.S. Gov't, Non-P.H.S.
  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Circadian Rhythm / genetics*
  • DNA-Binding Proteins / genetics*
  • Fungal Proteins
  • Gene Expression Regulation, Fungal / radiation effects*
  • Genes, Fungal
  • Light*
  • Molecular Sequence Data
  • Neurospora crassa / genetics*
  • Signal Transduction
  • Transcription Factors / genetics*

Substances

  • DNA-Binding Proteins
  • Fungal Proteins
  • Transcription Factors
  • wc-1 protein, Neurospora crassa

Associated data

  • GENBANK/AY050833
  • GENBANK/Y17722