Elements of a Fungal Light Receptor

Abstract

The fungus Neurospora crassa is a light-sensitive organism, but its photoreceptor has remained elusive. The prime candidate, a transcription factor called White Collar-1 (WC-1), is required for all responses to light (see the Perspective by Linden). By eliminating the part of the WC-1 protein that would be expected to bind a chromophore (the LOV, or light, oxygen, and voltage, domain), He et al. show that the LOV domain is required for light responses, but not for the circadian clock function of WC-1. They then identify flavin adenine dinucleotide (FAD) as the chromophore bound to WC-1. Froehlich et al. show that WC-1 acts (as a dimer with WC-2) on two light-responsive elements in the promoter of the clock component frequency (FRQ). By reassembling this system in vitro and inducing FRQ transcription with light, these authors show that WC-1 is the blue light photoreceptor for Neurospora. In their system as well, FAD must be added in order to observe light reception. H. Linden, A white collar protein senses blue light, Science 297, 777-778 (2002). [Summary] [Full Text] He, P. Cheng, Y. Yang, L. Wang, K. H. Gardner, Y. Liu, White Collar-1, a DNA binding transcription factor and a light sensor, Science 297, 840-843 (2002). [Abstract] [Full Text] C. Froehlich, Y. Liu, J. J. Loros, J. C. Dunlap, White Collar-1, a circadian blue light photoreceptor, binding to the frequency promoter, Science 297, 815-819 (2002). [Abstract] [Full Text]