Molecular mechanism of light responses in Neurospora: From light-induced transcription to photoadaptation

Qiyang He, Yi Liu

Research output: Contribution to journalArticle

151 Scopus citations

Abstract

Blue light regulates many molecular and physiological activities in a large number of organisms. In Neurospora crassa, a eukaryotic model system for studying blue-light responses, the transcription factor and blue-light photoreceptor WHITE COLLAR-1 (WC-1) and its partner WC-2 are central to blue-light sensing. Neurospora's light responses are transient, that is, following an initial acute phase of induction, light-regulated processes are down-regulated under continuous illumination, a phenomenon called photoadaptation. The molecular mechanism(s) of photoadaptation are not well understood. Here we show that a common mechanism controls the light-induced transcription of immediate early genes (such as frq, al-3, and vvd) in Neurospora, in which light induces the binding of identical large WC-1/WC-2 complexes (L-WCC) to the light response elements (LREs) in their promoters. Using recombinant proteins, we show that the WC complexes are functional without the requirement of additional factors. In vivo, WCC has a long period photocycle, indicating that it cannot be efficiently used for repeated light activation. Contrary to previous expectations, we demonstrate that the light-induced hyperphosphorylation of WC proteins inhibits bindings of the L-WCC to the LREs. We show that, in vivo, due to its rapid hyperphosphorylation, L-WCC can only bind transiently to LREs, indicating that WCC hyperphosphorylation is a critical process for photoadaptation. Finally, phosphorylation was also shown to inhibit the LRE-binding activity of D-WCC (dark WC complex), suggesting that it plays an important role in the circadian negative feedback loop.

Original languageEnglish (US)
Pages (from-to)2888-2899
Number of pages12
JournalGenes and Development
Volume19
Issue number23
DOIs
StatePublished - Dec 1 2005

Keywords

  • Circadian
  • LOV domain
  • Light
  • Phosphorylation
  • Photoadaptation
  • White collar-1

ASJC Scopus subject areas

  • Genetics
  • Developmental Biology

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