Control of cell-wall glucan degradation during development inSchizophyllum commune

Abstract

Cell-free extracts and culture fluids ofSchizophyllum commune were assayed for enzymatic activity effecting the degradation of an alkali-insoluble cell-wall component of this mushroom, a glucan containingβ-(1→3) linkages (R-glucan). The activity of R-glucanase as determinedin vitro with isolated R-glucan as a substrate was found to increase from the onset of pileus formation, a process accompanied by R-glucan degradation in the mycelium. This R-glucanase activity is influenced by the presence of glucose in the culture medium, probably through a mechanism by which glucose represses synthesis of the enzyme.

A morphological mutant (cup mutant) producing no pilei and exhibiting a lower degradation of R-glucanin vivo, produced levels of R-glucanase comparable to those of the wild-type stock and gave even higher levels in young cultures. The difference between the wild-type stock and the cup mutant with respect to degradation of R-glucan during development is most probably to be sought in the structure of the cell wall, the R-glucan in isolated cell walls of the cup mutant being less susceptible to enzymatic attack. High resistance to R-glucanase activity was also encountered in certain cell-wall preparations of the wild-type stock e.g. in those prepared from developing pilei. This suggests that cell-wall glucan degradation during pileus formation is controlled by both the level of R-glucanase, as influenced by glucose in the medium, and differences in protection of R-glucan in the cell wall against enzymatic attack.