Identification of a gene cluster for biosynthesis of the sesquiterpene antibiotic, heptelidic acid, in Aspergillus oryzae.

Heptelidic acid (HA), a sesquiterpene lactone, is a known inhibitor of glyceraldehyde-3-phosphate dehydrogenase (GAPDH). Recently, we found that HA was produced by Aspergillus oryzae RIB40 and acted as the growth inhibitor of the salt-tolerant lactic acid bacteria in soy sauce brewing. Although several decades have passed since the discovery of HA, the genes involved in its biosynthesis and biosynthetic pathway have not yet been fully identified. In this study, we identified the HA biosynthetic gene cluster (HA cluster) using gene disruption and expression analysis. We also revealed that two transcription regulatory genes adjacent to the HA cluster were responsible for the expression of HA biosynthetic genes in A. oryzae. Interestingly, the HA cluster contained a gene encoding GAPDH (gpdB), which showed much higher resistance to HA than the GAPDH gene (gpdA) located at the other locus, but which did not seem to act as a self-resistant gene.