Identification of a gene from Streptomyces rimosus M527 negatively affecting antibiotic biosynthesis and morphological differentiation

Abstract

Background: The polyene macrolide rimocidin, produced by Streptomyces rimosus M527, was found to be highly effective against a broad range of fungal plant pathogens. Current understanding of the regulatory mechanism of rimocidin biosynthesis and morphological differentiation in S. rimosus M527 is limited. NsdA is considered as a negative regulator involved in morphological differentiation and biosynthesis of secondary metabolites in some Streptomyces.Results: In this study, nsdAsr was cloned from S. rimosus M527. The role of nsdAsr in rimocidin biosynthesis and morphological differentiation was investigated by gene deletion, complementation, and over-expression. A ΔnsdAsr mutant was obtained using CRISPR/Cas9. The mutant produced more rimocidin (46%) and generated more spores than the wild-type strain. Over-expression of nsdAsr led to a decrease in rimocidin production and impairment of sporulation. Quantitative reverse transcription-PCR (qRT-PCR) analysis revealed that transcription of rim genes responsible for rimocidin biosynthesis was up-regulated in the ΔnsdAsr mutant but down-regulated in the nsdAsr over-expression strain. Similar effects have been described for Streptomyces coelicolor M145 and the industrial toyocamycin-producing strain Streptomyces diastatochromogenes 1628.Conclusion: NsdAsr is identified as a negative regulator of sporluation and antibiotic biosynthesis as well as the transcription of biosynthetic genes both in its host S. rimosus M527 and in model strain S. coelicolor and industrial producer strain S. diastatochromogenes 1628. This work will provide further information for understanding regulatory mechanisms controlling rimocidin biosynthesis in S. rimosus M527.