FUNGAL ENZYMES DEGRADING PLANT-CELL WALLS - THEIR POSSIBLE SIGNIFICANCE IN THE ECTOMYCORRHIZAL SYMBIOSIS

There is increasing evidence that some ectomycorrhizal (ECM) fungi produce key enzymes required for degradation of plant cell wall components. We examine the evidence for these enzyme activities in the context of the structure of plant cell walls and what is known regarding their enzymic breakdown by other fungal groups. The normally intercellular nature of the ECM symbiosis requires that strict regulation of enzyme activity must exist at the fungus-root interface. The interface and extramatrical mycelium are identified as spatially separate phases of the ECM mycelium within which distinct developmental stages evince temporal differences in patterns of enzyme activity. Enzyme synthesis by ECM fungi is held to be regulated through the nutritional status of the mycelium: this status is considered to vary spatially and temporally, according to the nature of the substrates encountered by the mycelium and the metabolites provided by the host.