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

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.