Role of cyclophilin in fruiting body formation of Flammulina velutipes

To elucidate the physiological role of cyclophilin, which is expressed in l arge quantities in fruiting bodies of Flammulina velutipes, the effect of c yclosporin A (CsA), an inhibitor of cyclophilin, on vegetative growth and f ruiting body formation was studied. CsA had little effect on hyphal growth at 25 degreesC, but inhibited growth at 13 degreesC and 4 degreesC. Fruitin g body formation, which was initiated by a temperature shift from 25 degree sC to 13 degreesC or 4 degreesC, was also markedly delayed in the presence of CsA, indicating the stress-protein nature of cyclophilin. The results sh owed that cyclophilin could protect several kinds of proteins from losing t heir biological activity under a low temperature, by which fruit body forma tion was initiated. The effect of CsA on the growth of several microorganis ms was investigated. They could be classified into three groups in terms of the effect of CsA: (1) Escherichia coli, whose growth was not affected at all; (2) Fusarium oxysporum, Aspergillus niger, Pleurotus ostreatus, Pleuro tus cornucopiae and Pholiota nameko, whose growth was completely inhibited; and (3) F. velutipes, Schizosaccharomyces pombe and Saccharomyces cerevisi ae, whose growth was inhibited to some extent.