Functional analysis of a β-1,6-glucanase gene from the grass endophytic fungus Epichloë festucae

β-1,6-glucanases degrade the polysaccharide β-1,6-glucan, a cell wall component in some filamentous fungi. A single copy of a β-1,6-glucanase gene, designated gcnA, was identified in each of the grass endophytic fungi Neotyphodium lolii and Epichloë festucae. Phylogenetic analysis indicates that the GcnA protein is a member of glycosyl hydrolase family 5, and is closely related to fungal β-1,6-glucanases implicated in mycoparasitism. The E. festucae gcnA gene was expressed in mycelium grown in culture and in both vegetative and reproductive tissues of perennial ryegrass. A gcnA replacement mutant had reduced β-1,6-glucanase activity when grown in media containing pustulan as the major carbon source. β-1,6-glucanase activity was restored in the replacement mutant by introducing multiple copies of the gcnA gene. Growth of ΔgcnA and gcnA-overexpressing strains in vegetative grass tissues was indistinguishable from wild type strains.