The stress-response sigma factor σH controls the expression of ssgB, a homologue of the sporulation-specific cell division gene ssgA, in Streptomyces coelicolor A3(2)

Abstract

By using a previously established method for the identification of promoters recognized by a particular sigma factor of RNA polymerase, we identified a promoter in Streptomyces coelicolor A3(2) that is recognized by a heterologous RNA polymerase containing the late sporulation-specific sigma factor sigma(F). The promoter directed the expression of a gene named ssgB, which is related to the sporulation-specific cell division gene ssgA. These genes, together with three others, constitute a new family of paralogous genes specific for Streptomyces. S1-nuclease mapping using RNA prepared from an Escherichia coli strain that expresses ssgB under the control of sigma(F), and from S. coelicolor A3(2) at various developmental stages, identified identical transcription start points in both strains, corresponding to the promoter ssgBp. The promoter is developmentally regulated in S. coelicolor: it is induced at the time of aerial mycelium formation and is most active during sporulation. However, the level of the ssgB transcript was unaffected in a sigF mutant of S. coelicolor A3(2). Interestingly, the level of the transcript was substantially reduced in an S. coelicolor strain that was mutant for the sigH gene, which encodes a stress-response sigma factor (sigma(H)) that is essential for sporulation in S. coelicolor A3(2). This dependence of ssgB upon sigH was confirmed by an in vitro transcription assay, in which sigma(H), in the presence of the S. coelicolor core RNA polymerase, was able to recognize ssgBp. These results suggest that the S. coelicolor ssgB gene is under the control of the stress-response sigma(H). Transcription of ssgB was investigated in S. coelicolor A3(2) mutants with lesions in each of six known early whi genes required for sporulation septation. Expression of ssgB was deregulated in three of the mutants ( whiA, whiI, and whiJ). Based on these data, it is proposed that the ssgB gene product plays a role in the developmental process in S. coelicolor A3(2).

The SsgA-like proteins in actinomycetes: small proteins up to a big task

“…Transcription of ssgB is directed from a single promoter 52 nt upstream of the most likely ATG start codon, resulting in a protein of 137 aa. Expression occurs in a life-cycle dependent manner and is strongly activated towards sporulation (Kormanec and Sevcikova 2002 ). In an E. coli two-plasmid system the ssgB promoter was found to be active in the presence of several members of the SigB-like sigma factor family (i.e.…”

“…Expression of ssgB was unaffected in an sigF mutant of S. coelicolor , while in a sigH mutant no ssgB transcripts were detected. Furthermore, His-tagged σ H initiated transcription from the ssgB promoter in in vitro run-off transcription assays (Kormanec and Sevcikova 2002 ). However, since a sigH mutant of S. coelicolor still produced some spores (Sevcikova et al.…”

The dpsA Gene of Streptomyces coelicolor: Induction of Expression from a Single Promoter in Response to Environmental Stress or during Development

“…SigH is an obvious candidate to modulate such up-regulation as it is known to exert developmental control [10] and is also required for normal aerial development [9]. We performed qRT PCR experiments to monitor and compare dpsA expression in vegetative and aerial hyphae from S. coelicolor M145 and mutant strains ( sigH , sigK and sigF , all of which are known to be involved in aerial development).…”

Cascade of extracytoplasmic function sigma factors inMycobacterium tuberculosis: identification of a σJ-dependent promoter upstream ofsigI

“…The E. coli two‐plasmid system that was used for the identification of M. tuberculosis σ J ‐dependent promoters was successfully used for identification of regulons of several sigma factors from different bacteria (Kormanec & Sevcikova, 2002; Homerova et al , 2004a; Skovierova et al , 2006). The advantage of the system is that it allows identification of direct targets of a particular sigma in heterologous conditions that simulate induction of a sigma factor.…”