Fruiting body formation of mushrooms, a characteristically morphological differentiation observed in eukaryotic microorganisms, is affected by environmental factors. Especially, light is known to be one of the most important environmental signals and influences those fruiting body development. In Lentinula edodes (Shiitake), blue light is required for initiation of the fruiting body formation. Therefore, photoreceptors, which are capable of light stimuli, are important for adaptation to immediate environments. Blue light photoreceptors are generally divided into two distinct classes, phototropins and cryptochromes. We previously reported that PHRA/PHRB, a blue-light photoreceptor complex in L. edodes, could regulate the transcription of the tyrosinase gene in a light-dependent manner. The PHRA belongs to the phototropin family, no cryptochrome, however, has been identified in basidiomycetes.
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 fungi and plant. Gene expressions of Le.cry, phrA and phrB were analyzed by quantitative RT-PCR (Reverse Transcription Polymerase Chain Reaction) in vegetatively growing mycelia and during fruiting body formation (primordia, immature and mature fruiting bodies). As a result, the transcriptions of phrA and phrB were similar in all stages. Unlike phrA and phrB, Le.cry was most abundantly transcribed 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 of Le.cry and phrA/phrB suggest that Le.CRY might have a role different from the PHRA/PHRB complex during mycelial and fruiting body development.