CO2 control of fruiting in Schizophyllum commune: noninvolvement of sustained isocitrate lyase derepression

The activity of the enzyme, isocitrate lyase, was repressed in glucose cultures of Schizophyllum commune and derepressed in acetate-grown mycelium of this basidiomycetous fungus. The maximum acetate-derepressed level of this soluble enzyme was comparable in individual homokaryotic mycelium or in the dikaryon. Addition of CO2, NaHCO3, or CaCO3 did not significantly derepress isocitrate lyase activity in glucose-cultures. Neither normal dikaryotic fruiting nor its inhibition by carbon dioxide resulted in marked and sustained changes in isocitrate lyase. Thus, a fluctuation in isocitrate lyase activity does not appear to be the salient response of S. commune to increased CO2 tension.