Role of the Botrytis cinerea FKBP12 ortholog in pathogenic development and in sulfur regulation

The functional characterization of the FKBP12 encoding gene from the phytopathogenic fungus Botrytis cinerea was carried out. B. cinerea genome sequence owns a single ortholog, named BcFKBP12, encoding a FK506-binding protein of 12 kDa. BcFKBP12 mediates rapamycin sensitivity both in B. cinerea and in Saccharomyces cerevisiae, a property unique to FKBP12 proteins, probably via the inhibition of the protein kinase TOR (target of rapamycin). The relative abundance of the prolyl isomerase appeared to be regulated and increased in response to the presence of extracellular nutrients. Surprisingly, the BcFKBP12 deletion did not affect the pathogenic development of the strain B05.10, while it was reported to cause a reduction of the virulence of the strain T4. We report for the first time the BcFKBP12 involvement in the sulfur repression of the synthesis of a secreted serine protease. Rapamycin treatment did not relieve the sulfur repression of the reporter system in the wild-type strain. Thus BcFKBP12 may participate in sulfur regulation and its contribution seems to be independent of TOR.