The Effect of Light on Fruiting Body Formation and Adenosine 3′:5′-Cyclic Monophosphate Metabolism in <i>Coprinus macrorhizus</i>

The monokaryotic mycelia of a mutant strain, fis(c), of Coprinus macrorhizus, which are able to form monokaryotic fruiting bodies in the light, failed to form any fruiting bodies in darkness. A dikaryon and a mutant strain, ds, formed malformed fruiting bodies in darkness. Illumination for 1 day of fis(c) mycelia grown in darkness for 4 days or longer was effective in inducing malformed fruiting bodies. The accumulation of adenosine 3':5'-cyclic monophosphate in the illuminated mycelia of strain fis(c) was demonstrated. The illuminated mycelia of strain fis(c) produced high levels of adenylate cyclase [ATP pyrophosphate-lyase (cyclizing), EC 4.6.1.1] and phosphodiesterase (3':5'-cyclic-AMP 5'-nucleotidohydrolase, EC 3.1.4.17), which degrades cAMP, while the dark-grown mycelia showed no or very low activities of these enzymes. Dikaryotic mycelia and monokaryotic mycelia of strain ds produced significant amounts of these enzymes even in darkness. When the dark-grown mycelia of strain fis(c) were exposed to continuous light, the activities of adenylate cyclase and phosphodiesterase increased rapidly after a lag period whose length depends on the culture age of mycelia. Cycloheximide inhibited the increase in these enzyme activities stimulated by light. When the fis(c) mycelia were exposed to continuous light, an increase in cAMP-binding activity was observed. A possible participation of cAMP in the formation of fruiting bodies in C. macrorhizus is discussed.