Effect of antibiotic down-regulatory gene wblA ortholog on antifungal polyene production in rare actinomycetes Pseudonocardia autotrophica.

The rare actinomycete Pseudonocardia autotrophica was previously shown to produce a solubilityimproved toxicity-reduced novel polyene compound named Nystatin-like Pseudonocardia Polyene (NPP). The low productivity of NPP in P. autotrophica implies that its biosynthetic pathway is tightly regulated. In this study, wblApau was isolated and identified as a novel negative regulatory gene for NPP production in P. autotrophica, which showed approximately 49% amino acid identity with a global antibiotic down-regulatory gene, wblA, identified from various Streptomycetes species. Although no significant difference in NPP production was observed between P. autotrophica harboring empty vector and the S. coelicolor wblA under its native promoter, approximately 12% less NPP was produced in P. autotrophica expressing the wblA gene under the strong constitutive ermE(*) promoter. Furthermore, disruption of the wblApau gene from P. autotrophica resulted in an approximately 80% increase in NPP productivity. These results strongly suggest that identification and inactivation of the global antibiotic down-regulatory gene wblA ortholog are a critical strategy for improving secondary metabolite overproduction in not only Streptomyces but also non-Streptomyces rare actinomycete species.