Regulation of transcription by light in Neurospora crassa: A model for fungal photobiology?

• Neurospora crassa detects light stimuli and responds to them.
• Light responses are mediated by light-activated White Collar Complex (WCC).
• The WCC changes chromatin structure resulting in activation of transcription.
• The activation of transcription by light is transient, leading to photoadaptation.
• The photoreceptor VVD plays a major role in photoadaptation in Neurospora.

Neurospora crassa is used as a model to investigate the molecular mechanisms of fungal light responses. The effects of light in Neurospora include development of asexual spores and sexual structures, biosynthesis of photoprotective pigments in mycelia, and entrainment of the circadian clock. These effects are mediated by the White Collar Complex (WCC), which activates the transcription of genes. The transcription factor WHITE COLLAR-1 (WC-1) is a blue-light photoreceptor that interacts with WHITE COLLAR-2 (WC-2) to form the WCC. Upon light exposure WCC homodimers assemble on the promoters of genes to activate transcription. One of these genes encodes another blue-light photoreceptor, VIVID (VVD), which then binds to light-activated WC-1. VVD binding to WC-1 disrupts transcriptionally active WCC dimers, resulting in an attenuation of the activation of transcription.