Laccase (Lcc; EC 1.10.3.2) belongs to a group of polyphenol oxidases, which catalyzed the oxidation of single-electron from phenolic substrates or aromatic amines. Many organisms possess several lcc encoding genes, and their biological functions diverge into many branches. There are many studies on biochemical function of Lccs, however, there are few studies about biological functions of one Lcc in detail. We researched on biological function of Lcc1, which is most abundantly secreted enzyme from vegetative mycelia into liquid culture in L. edodes. In our previous study, lcc1 gene was down regulated by RNAi method in L. edodes, and then ivrL1#32 was selected as a completely lcc1 dowaregulated transformant. We revealed that fruiting body development in ivrL1#32 was significantly suppressed compared to wild type strain. In this study, we observed the hyphal morphology of ivrL1#32. IvrL1#32 did not form thick aerial mycelium mat when grown on MYPG agar plate. From the observation using scanning electron microscope (SEM), hyphae of ivrL1#32 had many abnormal short branches and their mycelial density was lower than that of wild type strain. From transmission electron microscope observation (TEM), ivrL1#32 lacked obviously distinguishable outer and inner layer in their cell wall. In addition, the fibrous layer of ivrL1#32, which connected hyphae, obviously decreased. These morphological phenotypes would be caused by the absence of Lcc1 in L. edodes. Our results provide a clue to resolve of the biological function of Lcc1 in L. edodes.

• Keiko Nakade(Iwate Biotechnology Research Center, 22-174-4 Narita, Kitakami, Iwate 024-0003, Japan)
• Yuichi Sakamoto( Iwate Biotechnology Research Center, 22-174-4 Narita, Kitakami, Iwate 024-0003, Japan) | Yuichi Sakamoto