Cell wall structure of secreted laccase-silenced strain in Lentinula edodes

Laccase1 (Lcc1) is abundantly secreted from vegetative mycelia into culture medium by Lentinula edodes. Down-regulation of lcc1 in L. edodes results in abnormal hyphal structure and thinner cell wall in mycelia. In this study, we observed the effects of Lcc1 on the hyphal morphology and cell wall structure of L. edodes. A thick cell wall and fibrous layer were clearly observed in the lcc1-silenced strain ivrL1#32, when purified Lcc1 (0.1 mU/mL) was added to the culture medium. The ratio of cell wall polysaccharide contents was compared between the ivrL1#32 strain and the wild-type (WT) strain SR-1, revealing that levels of the alkali soluble β-1,3-1,6-glucan were significantly lower in the lcc1-silenced strain than in the WT strain. Chronological analysis revealed that chitin content in the cell wall did not increase over time, but that the alkali soluble β-1,3-1,6-glucan content increased after Lcc1 secretion in the WT. Taken together, these data suggest that the increased level of β-1,3-1,6-glucan induced by Lcc1 in the mycelial cell wall contributes to increased cell wall thickness and strength.