AbstractBackgroundViriditoxin is one of the ‘classical’ secondary metabolites produced by fungi and that has antibacterial and other activities; however, the mechanism of its biosynthesis has remained unknown.ResultsHere, a gene cluster responsible for its synthesis was identified, using bioinformatic approaches from two species that produce viriditoxin and then through gene disruption and metabolite profiling. All eight genes in the cluster inPaecilomyces variotiiwere mutated, revealing their roles in the synthesis of this molecule and establishing its biosynthetic pathway which includes an interesting Baeyer-Villiger monooxygenase catalyzed reaction. Additionally, a candidate catalytically-inactive hydrolase was identified as being required for the stereoselective biosynthesis of (M)-viriditoxin. The localization of two proteins were assessed by fusing these proteins to green fluorescent protein, revealing that at least two intracellular structures are involved in the compartmentalization of the synthesis steps of this metabolite.ConclusionsThe full pathway for synthesis of viriditoxin was established by a combination of genomics, bioinformatics, gene disruption and chemical analysis processes. Hence, this work reveals the basis for the synthesis of an understudied class of fungal secondary metabolites and provides a new model species for understanding the synthesis of biaryl compounds with a chiral axis.
Author response: Targeted induction of a silent fungal gene cluster encoding the bacteria-specific germination inhibitor fumigermin
