Identification of the Sesquiterpene Cyclase Involved in the Biosynthesis of (+)-4-Epi-eremophil-9-en-11-ol Derivatives Isolated from .

Cultivation of the phytopathogenic fungus using sublethal amounts of copper sulfate yielded a cryptic sesquiterpenoids family, which displayed the basic chemical structure of (+)-4-epi-eremophil-9-ene. The biosynthesis pathway was established, and the route involved the likely transformation of the diphosphate of farnesyl (FDP), to give a -fused eudesmane cation, through ()-hedycaryol, finally yielding the (+)-4-epi-eremophil-9-enol derivatives. An expression study of genes that code for the sesquiterpene cyclases (STC), including the recently reported gene present in the genome, was performed in order to establish the STC involved in this biosynthesis. The results showed a higher expression level for the gene with respect to the other genes in both wild-type strains, B05.10 and UCA992. Deletion of the gene eliminated (+)-4-epi-eremophilenol biosynthesis, which could be re-established by complementing the null mutant with the gene. Chemical analysis suggested that STC7 is the principal enzyme responsible for the key step of cyclization of FDP to eremophil-9-en-11-ols. Furthermore, a thorough study of the two wild-types and the complemented mutant revealed four new eremophilenol derivatives whose structures are reported here.