Molecular Basis of Fruiting-body Formation in Basidiomycete Fungus

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Fruiting-body formation of basidiomycetes is one of the most typical and attractive morphological differentiation observed in microorganisms. To understand the molecular mechanisms of fruiting-body formation in Lentinula edodes (Shiitake), we have studied on the target genes of two DNA-binding transcription factors PRIB and Le.CDC5, both of which regulate the fruiting-body formation. The PRIB protein binds to a 16-bp sequence with the consensus sequence of 5'GGGGGGGACAGGANCC3' and the Le.CDC5 protein binds to a 7-bp sequence with theconsensus sequence 5'GCAATGT3'. MfbA is also interesting protein that regulates the fruiting-body formation and possesses RGD sequence, PHD finger and SET domain. So we studied properties of MfbA protein. Concerning the PRIB, Le.CDC5 and MfbA, we obtained the following results. (1)The three target genes were identified for PRIB protein, ie., priB, uck1 (UMP-CMP kinase genes) and mfbC, the homologue of Saccharomyces cerevisiae YJRO070c. The mfbC gene is cons … More idered to encode the protein interacting to a putative translation initiation factor eIF5A. Only mature fruiting body was shown to contain the transcript of the mfbC gene almost exclusively, suggesting that mfbC may play a role at the final stage of fruiting-body formation. The mfbC transcript showed a region-specific distribution in hymenophore (gill tissue). High level of the mfbC transcript was detected in the outer region of trama, which is the region branching out into subhymenium. (2)We isolated two (3.7-kb and 3.9-kb) genomic HindIII fragments, to which Le.CDC5 protein binds. The two fragments contained several 7-bp consensus-like sequences and Le.CDC5 protein bound to them. They contained two or three genes of which functions were unknown. (3)The PHD finger-containing fragment of MFBA protein was found to bind to a 7-bp sequence with the consensus sequence of 5'ANAAGGT3'. Computer searching gave the information that the SET domain may be related to the methylase activity for the lysine residues of histone H3. These imply the possibility that MFBA protein may be a sort of chromatin-remodelling protein. Less