Involvement of protein kinase C in the response of Neurospora crassa to blue light

Abstract

As a first step towards understanding the process of blue light perception, and the signal transduction mechanisms involved, in Neurospora crassa we have used a pharmacological approach to screen a wide range of second messengers and chemical compounds known to interfere with the activity of well-known signal transducing molecules in vivo. We tested the influence of these compounds on the induction of the al-3 gene, a key step in light-induced carotenoid biosynthesis. This approach has implicated protein kinase C (PKC) as a component of the light transduction machinery. The conclusion is based on the effects of specific inhibitors (calphostin C and chelerythrine chloride) and activators of PKC (1,2-dihexanoyl-sn-glycerol). During vegetative growth PKC may be responsible for desensitization to light because inhibitors of the enzyme cause an increase in the total amount of mRNA transcribed after illumination. PKC is therefore proposed here to be an important regulator of transduction of the blue light signal, and may act through modification of the protein White Collar-1, which we show to be a substrate for PKC in N. crassa.

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

“…3) suggests that, unlike the phototropins, most of the WC-1 cannot recover back to the dark state after its photoactivation. The in vivo experiments showed that, although Neurospora is insensitive to a second light if given <1 h of dark recovery time (Schrott 1981;Arpaia et al 1999;Schwerdtfeger and Linden 2001), WCC can respond to a second light pulse after >1 h in DD (Fig. 4).…”

“…Cold Spring Harbor Laboratory Press on March 31, 2019 -Published by genesdev.cshlp.org Downloaded from <1 h after the first one (Schrott 1981;Arpaia et al 1999;Schwerdtfeger and Linden 2001).…”

“…In Neurospora, after the initial rapid induction of lightinducible genes, the responses quickly decrease and stay at low levels (Schrott 1981;Arpaia et al 1999;Heintzen et al 2001;Schwerdtfeger and Linden 2001;Shrode et al 2001), the results of light insensitivity. Similar to the kinetics of the induction of immediate-early genes, WC proteins first become hyperphosphorylated after 15-30 min in LL, and then the levels of their phosphorylation decrease and are maintained at levels that are higher than those in DD (Talora et al 1999;Schwerdtfeger andLinden 2000, 2001;Cheng et al 2003a;He et al 2005).…”

“…In Neurospora, despite the continuous presence of light, levels of immediate light-induced genes quickly decrease to relatively low levels after 2 h in constant light (LL) (Schrott 1981;Arpaia et al 1999;Cheng et al 2001a;Schwerdtfeger and Linden 2001;Shrode et al 2001). In addition, shifting Neurospora from low-to high-intensity light can trigger a second light induction (Arpaia et al 1999;Schwerdtfeger and Linden 2001). These photoadaptative responses are typical for Neurospora and similar to adaptive responses in vertebrates (Pugh Jr. et al 1999).…”

“…At the molecular level, the mechanism for photoadaptation is not well understood in Neurospora, although VVD and protein kinase C (PKC) have been implicated in this process (Arpaia et al 1999;Heintzen et al 2001;Schwerdtfeger and Linden 2001;Shrode et al 2001;Franchi et al 2005). VVD is a small protein consisting mostly of a single LOV domain and is another blue-light photoreceptor (Cheng et al 2003a;Schwerdtfeger and Linden 2003) that acts as a repressor of light responses.…”