Light signaling networks revealed by genome-wide mapping of direct targets for Neurospora WHITE COLLAR-2

Light signaling pathways and circadian clocks are inextricably linked and have profound effects on behavior in most organisms. Here we used ChIP-sequencing to uncover direct targets of the Neurospora crassa circadian regulator White Collar Complex (WCC). The WCC is a blue-light receptor and the key transcription factor of the circadian oscillator. It controls a transcriptional network that regulates ~20% of all genes generating daily rhythms and responses to light. We found that in response to light, WCC binds to hundreds of genomic regions, including the promoters of previously identified clock- and light-regulated genes. We show that WCC directly controls the expression of 24 transcription factor genes, including the clock-controlled adv-1 gene found to reside in a circadian output pathway required for daily rhythms in development. Our findings provide links between the key circadian activator and effectors in downstream regulatory pathways.