Cross-Recognition of Promoters by the Nine SigB Homologues Present in <i>Streptomyces coelicolor</i> A3(2)

• Main Authors: Beatrica Sevcikova, Bronislava Rezuchova, Vladimira Mazurakova, Dagmar Homerova, Renata Novakova, Lubomira Feckova, Jan Kormanec
• Format: Article
• Language: English
• Published: MDPI AG 2021-07-01
• Series: International Journal of Molecular Sciences
• Subjects: differentiation; promoter; regulation; sigma factor; <i>Streptomyces</i>; stress response
• Online Access: https://www.mdpi.com/1422-0067/22/15/7849
• ISSN: 1661-6596; 1422-0067

In contrast to <i>Bacillus subtilis</i>, <i>Streptomyces coelicolor</i> 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 <i>S. coelicolor</i> A3(2). Here, we used this system to identify 14 promoters recognized by SigB. The promoters were verified in vivo in <i>S. coelicolor</i> A3(2) under osmotic stress conditions in <i>sigB</i> and <i>sigH</i> 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 <i>sigB</i> and <i>sigH</i> operon mutants in <i>S. coelicolor</i> 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 <i>S. coelicolor</i> A3(2).