Shining a light on mushroom formation: The influence of light in the fructification process of Schizophyllum commune

Abstract

Light and ambient CO₂ are the main factors regulating mushroom formation in many fungi, among which the model organism Schizophyllum commune. Blue light is known to stimulate fructification through the White Collar Complex (WCC), which functions as a transcription factor upon activation by blue light, while a consensus about the role of the red and far-red light sensing phytochrome has not yet been reached. In this research, an attempt has been made to identify a link between the light sensing pathway and the CO₂ sensing pathway in S. commune. It was shown that S. commune is able to fructify in the dark when ambient CO₂ levels are low. Deletion strains of the proteins forming the WCC did not show fructification under these conditions, implying that the presence of the WCC is necessary. The enzyme carbonic anhydrase was hypothesized to be a key player in the link between the light and CO₂ sensing pathway, where the WCC would inhibit expression of carbonic anhydrase. This has been investigated using qPCR. However, the inhibition of carbonic anhydrase expression upon light exposure has not been found in this study. Furthermore, the role of the phytochrome in the fructification process has been investigated by creating a phytochrome deletion strain. This strain showed reduced vegetative growth and an accelerated fructification response to white light. This implies a repressing role of the phytochrome on fructification. Results of red and far-red light experiments further insinuated that the phytochrome might be activated by far-red light rather than red light. These results could be valuable for the mushroom industry, by suggesting optimal light regimes to increase mushroom yield.