White Collar-1, a DNA Binding Transcription Factor and a Light Sensor

Abstract

Blue light regulates many physiological processes in fungi, but their photoreceptors are not known. In Neurospora crassa, all light responses depend on the Per-Arnt-Sim (PAS) domain-containing transcription factor white collar-1 (wc-1). By removing the WC-1 light, oxygen, or voltage domain, a specialized PAS domain that binds flavin mononucleotide in plant phototropins, we show that light responses are abolished, including light entrainment of the circadian clock. However, the WC-1-mediated dark activation of frq remains normal in this mutant, and the circadian clock can be entrained by temperature. Furthermore, we demonstrate that the purified Neurospora WC-1-WC-2 protein complex is associated with stoichiometric amounts of the chromophore flavin-adenine dinucleotide. Together, these observations suggest that WC-1 is the blue-light photoreceptor for the circadian clock and other light responses in Neurospora.

Reproduction without sex: conidiation in the filamentous fungus Trichoderma

“…Both BLR and WC proteins contain conserved Per-ARNT-Sim (PAS) domains, which have been shown to be involved in signal transduction through monitoring of the energy state of the cell, in protein-protein interactions and in the sensing of environmental signals (Möglich et al, 2009;Taylor & Zhulin 1999). In N. crassa, WC-1 and WC-2 (White Collar 1 and White Collar 2) mediate all known light responses (Ballario et al, 1996;Cheng et al, 2003;Degli-Innocenti & Russo, 1984;Froehlich et al, 2002;Harding & Turner, 1981;He et al, 2002;Herrera-Estrella & Horwitz, 2007;Linden & Macino, 1997). However, in T. atroviride, there appear to be both BLR-dependent and -independent blue-light perception pathways (Berrocal-Tito et al, 2000;CasasFlores et al, 2006;Rocha-Ramirez et al, 2002;Schmoll et al, 2010).…”

Molecular mechanism of light responses in Neurospora: from light-induced transcription to photoadaptation

“…His-tagged proteins were purified with a nickel column. Fluorescence spectra analyses and TLC were performed as previously described (He et al 2002).…”

“…A wc-1 RIP strain (He et al 2002) was used as the host strain for his-3 targeting a qa-wc1-2 construct (Cheng et al 2001b). Cultures were grown in minimal medium (1× Vogel's, 2% glucose) unless specified.…”

“…Neurospora crassa is one of the best understood model organisms for understanding blue-light responses in fungi and blue-light sensing in general Liu 2003;Liu et al 2003). In Neurospora, all known light responses are mediated by blue light, and almost all responses require the protein products of two genes, white collar-1 (wc-1) and wc-2 (Degli Innocenti and Russo 1984;Lakin-Thomas et al 1990;Collett et al 2002;He et al 2002;Lee et al 2003). The cloning of the two wc genes by Macino and coworkers (Ballario et al 1996; revealed that they are both PER-ARNT-SIM (PAS) domaincontaining transcription factors with GATA type Zn-finger DNA-binding domains.…”

“…The most N-terminal PAS domain of WC-1 belongs to a specialized class of PAS domains known as LOV (light, oxygen, or voltage) domains (Crosthwaite et al 1997;He et al 2002;Cheng et al 2003a). We and others have shown that, similar to the well-studied phototropins in plants (Briggs and Christie 2002), the LOV domain of WC-1 is associated with a flavin and functions as a bluelight photoreceptor in Neurospora (Froehlich et al 2002;He et al 2002). However, in contrast to phototropins, the LOV domain of WC-1 binds to FAD instead of FMN (flavin mononucleotide) and contains a significant extension in the loop connecting the ␣ЈA and ␣C helices.…”