Cross-Recognition of Promoters by the Nine SigB Homologues Present in Streptomyces coelicolor A3(2).

Beatrica Sevcikova,Vladimira Mazurakova,Dagmar Homerova,Jan Kormanec,Lubomira Feckova,Renata Novakova,Bronislava Rezuchova

doi:10.3390/ijms22157849

Beatrica Sevcikova, Vladimira Mazurakova + Show 5 more

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https://doi.org/10.3390/ijms22157849

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Abstract

In contrast to Bacillus subtilis, Streptomyces coelicolor A3(2) contains nine homologues of stress response sigma factor SigB with a major role in differentiation and osmotic stress response. The aim of this study was to further characterize these SigB homologues. We previously established a two-plasmid system to identify promoters recognized by sigma factors and used it to identify promoters recognized by the three SigB homologues, SigF, SigG, and SigH from S. coelicolor A3(2). Here, we used this system to identify 14 promoters recognized by SigB. The promoters were verified in vivo in S. coelicolor A3(2) under osmotic stress conditions in sigB and sigH operon mutants, indicating some cross-recognition of these promoters by these two SigB homologues. This two-plasmid system was used to examine the recognition of all identified SigB-, SigF-, SigG-, and SigH-dependent promoters with all nine SigB homologues. The results confirmed this cross-recognition. Almost all 24 investigated promoters were recognized by two or more SigB homologues and data suggested some distinguishing groups of promoters recognized by these sigma factors. However, analysis of the promoters did not reveal any specific sequence characteristics for these recognition groups. All promoters showed high similarity in the -35 and -10 regions. Immunoblot analysis revealed the presence of SigB under osmotic stress conditions and SigH during morphological differentiation. Together with the phenotypic analysis of sigB and sigH operon mutants in S. coelicolor A3(2), the results suggest a dominant role for SigB in the osmotic stress response and a dual role for SigH in the osmotic stress response and morphological differentiation. These data suggest a complex regulation of the osmotic stress response in relation to morphological differentiation in S. coelicolor A3(2).

Highlights

Gram-positive bacteria of the genus Streptomyces are one of the best producers of biologically active secondary metabolites with a wide range of activities. These filamentous bacteria undergo a complex process of morphological differentiation
Of the nine SigB homologues in S. coelicolor A3(2), only two, SigB and SigH, contain an operon with a validated anti-sigma factor gene, rsbB, rsbA, sigB [22,23] and ushY, ushX, sigH [28,31], partially similar to the B. subtilis sigB operon
They are thought to play a dual role in morphological differentiation and the osmotic stress response

Summary

Introduction

Gram-positive bacteria of the genus Streptomyces are one of the best producers of biologically active secondary metabolites with a wide range of activities (antibacterial, antitumor, antifungal, herbicidal, immunosuppressive, and anthelmintic). These filamentous bacteria undergo a complex process of morphological differentiation. Cytological, and biochemical approaches have indicated that a programmed cell death process takes place in the substrate mycelium to provide nutrients for aerial mycelium growth. These aerial hyphae grow by tip extension. They undergo a process of synchronous septation to unigenomic pre-spore compartments, which maturate into spores with a characteristic color [1,2]

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