Identification of butenolide regulatory system controlling secondary metabolism in Streptomyces albus J1074

Yousra Ahmed,Elke Brötz,Andriy Luzhetskyy,Bogdan Tokovenko,Yuriy Rebets

doi:10.1038/s41598-017-10316-y

Abstract

A large majority of genome-encrypted chemical diversity in actinobacteria remains to be discovered, which is related to the low level of secondary metabolism genes expression. Here, we report the application of a reporter-guided screening strategy to activate cryptic polycyclic tetramate macrolactam gene clusters in Streptomyces albus J1074. The analysis of the S. albus transcriptome revealed an overall low level of secondary metabolism genes transcription. Combined with transposon mutagenesis, reporter-guided screening resulted in the selection of two S. albus strains with altered secondary metabolites production. Transposon insertion in the most prominent strain, S. albus ATGSal2P2::TN14, was mapped to the XNR_3174 gene encoding an unclassified transcriptional regulator. The mutant strain was found to produce the avenolide-like compound butenolide 4. The deletion of the gene encoding a putative acyl-CoA oxidase, an orthologue of the Streptomyces avermitilis avenolide biosynthesis enzyme, in the S. albus XNR_3174 mutant caused silencing of secondary metabolism. The homologues of XNR_3174 and the butenolide biosynthesis genes were found in the genomes of multiple Streptomyces species. This result leads us to believe that the discovered regulatory elements comprise a new condition-dependent system that controls secondary metabolism in actinobacteria and can be manipulated to activate cryptic biosynthetic pathways.

Highlights

The genomics era in actinobacteria research has led to rapid changes in our understanding of secondary metabolite diversity[1, 2]
Secondary metabolism gene clusters in S. albus are poorly transcribed under laboratory conditions
A manual correction of the AntiSMASH 2.0 outcome of S. albus J1074 genome analysis resulted in a list of 26 secondary metabolite biosynthetic gene clusters (BGCs) by removing two regions (XNR_0391-0405 and XNR_2192) and adding the recently identified paulomycin BGC (XNR_0573-0610)[11]

Summary

Introduction

The genomics era in actinobacteria research has led to rapid changes in our understanding of secondary metabolite diversity[1, 2]. This approach is based on a simple assumption that the yield of the final metabolite directly correlates with the expression level of the corresponding biosynthetic gene cluster This strategy was successfully applied in the selection of Aspergillus terreus strains with increased titers of lovastatin[27] and was later adapted to screen for S. clavuligerus mutants with improved clavulanic acid production[28]. We report the further development and exploitation of this technique by combining it with transposon mutagenesis in S. albus J1074 This method enables fast and simple identification and characterization of the DNA locus responsible for the activation and production of the desired metabolite, providing insights into the regulatory processes silencing the secondary metabolism in actinobacteria

Methods

Results

Conclusion