Fruiting body formation in mushrooms, a characteristically morphological development observed in eukaryotic microorganisms, is triggered by environmental factors. Especially, light is one of the most important environmental signals that strongly influence fruiting development. Photoreceptors, which can recognize environmental light stimuli, are important molecules for adaptation to immediate environmental transitions. In the basidiomycetous fungus Lentinula edodes (Shiitake), blue light is essential for initiation of the fruiting body formation. We previously reported that the transcription of the tyrosinase gene involved with fruiting body formation in L. edodes appeared to depend upon PHRA/PHRB, a blue-light photoreceptor complex, in a light-dependent manner. Blue light photoreceptors in several organisms are generally divided into two distinct classes, phototropins and cryptochromes. The PHRA belongs to the phototropin family, no cryptochrome, however, has been identified in basidiomycetous fungi.
In this study, we report the isolation of a cryptochrome-encoding gene in L. edodes, designated Le.cry. The Le.cry gene encoded 606 amino acids (Le.CRY) containing characteristic domains for a DNA photolyase and a FAD binding, which are commonly found in DNA photolyase. Le.CRY was homologous to the cryptochrome dash family proteins in other species. Gene expressions of Le.cry, phrA and phrB in vegetatively growing mycelia and during fruiting body formation (primordia, immature and mature fruiting bodies) were quantitatively analyzed . As a result, the gene transcriptions of phrA and phrB were similar in all stages (Fig. 1.). Unlike phrA and phrB, Le.cry was most abundantly expressed in vegetatively growing mycelia. These results imply that Le.CRY appears to work predominantly in vegetatively growing mycelia, which is the preceding state of fruiting body formation. The differential expressions between Le.cry and phrA/phrB suggest that Le.CRYplay a role different from the PHRA/PHRB blue-light photoreceptor complex during mycelial and fruiting body development.