Roles for WHITE COLLAR-1 in circadian and general photoperception in Neurospora crassa.

The transcription factors WHITE COLLAR-1 (WC-1) and WHITE COLLAR-2 (WC-2) interact to form a heterodimeric complex (WCC) that is essential for most of the light-mediated processes in Neurospora crassa. WCC also plays a distinct non-light-related role as the transcriptional activator in the FREQUENCY (FRQ)/WCC feedback loop that is central to the N. crassa circadian system. Although an activator role was expected for WC-1, unanticipated phenotypes resulting from some wc-1 alleles prompted a closer examination of an allelic series for WC-1 that has uncovered roles for this central regulator in constant darkness and in response to light. We analyzed the phenotypes of five different wc-1 mutants for expression of FRQ and WC-1 in constant darkness and following light induction. While confirming the absolute requirement of WC-1 for light responses, the data suggest multiple levels of control for light-regulated genes.