Photoregulated tyrosinase gene in Polyporus arcularius

tyr1, the gene for tyrosinase, which is related to pigmentation of mycelia in dikaryotic strains, has been cloned and characterized from the basidiomycete Polyporus arcularius. The gene was present in a single copy in the genome. The putative amino acid sequence of Tyr1 was very similar to that of gLeTyr from Lentinula edodes. However, the carboxy-terminal region of the amino acid sequence of Tyr1 was variable among L. edodes, Agaricus bisporus, and this fungus. In the 5′-untranslated region near the initiation codon, a consensus sequence to the Dof1 binding site that is involved in light-regulated gene expression in maize was found. Transcription of tyr1 was photoregulated; transcription of tyr1 in P. arcularius was activated in light mycelia and inactivated in the dark mycelia. These results suggest that tyr1 is a light-regulated gene regulated by a Dof-like transcription factor in P. arcularius. Although the enzyme activity was observed only in a dikaryon, tyr1 was transcripted in both dikaryotic and monokaryotic strains. Thus, activation of the precursor of Tyr1 may require a posttranslational processing event that is developmentally regulated.