Physical interaction between VIVID and white collar complex regulates photoadaptation in Neurospora

摘要

Photoadaptation, the ability to attenuate a light response on prolonged light exposure while remaining sensitive to escalating changes in light intensity, is essential for organisms to decipher time information appropriately, yet the underlying molecular mechanisms are poorly understood. In Neurospora crassa, VIVID (VVD), a small LOV domain containing blue-light photoreceptor protein, affects photoadaptation for most if not all light-responsive genes. We report that there is a physical interaction between WD and the white collar complex (WCC), the primary blue-light photoreceptor and the transcription factor complex that initiates light-regulated transcriptional responses in Neurospora. Using two previously characterized WD mutants, we show that the level of interaction is correlated with the level of WCC repression in constant light and that even light-insensitive WD is sufficient partly to regulate photoadaptation in vivo. We provide evidence that a functional GFP-WD fusion protein accumulates in the nucleus on light induction but that nuclear localization of WD does not require light Constitutively expressed WD alone is sufficient to change the dynamics of photoadaptation. Thus, our results demonstrate a direct molecular connection between two of the most essential light signaling components in Neurospora, WD and WCC, illuminating a previously uncharacterized process for light-sensitive eukaryotic cells.