Abstract
Rhizoctonia solani isolates capable of forming sclerotia accumulated two or three times higher amounts of adenosine 3', 5'-cyclic monophosphate (cAMP) in mycelial cells comparing with those incapable of forming sclerotia. The addition of adenine and L-cysteine to culture media was effective to inhibit formation of sclerotia. Adenine inhibited adenylate cyclase activity, but not phosphodiesterase activity. L-cysteine showed no effect on both adenylate cyclase and phosphodiesterase activities. A single cAMP-receptor protein was detected by photoaffinity labeling with 8-N3-cAMP in mycelial extracts of all isolates of R. solani tested. The protein had an apparent molecular weight of 50, 000 and co-chromatographed on a DEAE-Sephacel column with cAMP-dependent protein kinase. The result indicated that the 50, 000-dalton protein may be a regulatory subunit of protein kinase with capacity to bind cAMP.
