Developmental regulation of the Streptomyces lividans ram genes: involvement of RamR in regulation of the ramCSAB operon.
Streptomycetes are filamentous soil bacteria that produce spores through a complex process of morphological differentiation. The ram cluster plays an important part during the development. The ram genes encode a membrane-bound kinase (RamC), a small protein (RamS), components of an ABC transporter (RamAB), and a response regulator (RamR). While the introduction of an extra copy of the ram cluster accelerates development in Streptomyces lividans, ramABR disruption mutants are unable to produce aerial hyphae and spores. The developmental regulation of ram gene transcription was analyzed. Transcription of the ram genes occurred only on solid rich media and not on minimal media. The ramR gene is transcribed from a single promoter during all growth stages, with the highest levels during aerial growth. The ramCSAB genes comprise one operon and are transcribed from one principal promoter, P1, directly upstream of ramC. Transcription of ramCSAB was already observed during vegetative growth, but was strongly upregulated upon initiation of formation of aerial hyphae and was decreased during late stages of development. A large inverted repeat located downstream of ramS terminated the majority of transcripts. The introduction of ramR on a multicopy vector in S. lividans strongly induced P1 activity, while disruption of this regulator eliminated all P1 promoter activity. This shows that ramR is a crucial activator of ramCSAB transcription. Importantly, in bldA, bldB, bldD, or bldH mutants, ramR and ramCSAB are not transcribed, while ram gene transcription was observed in the earliest whi mutant, whiG. This indicates that the transcription of the ram genes marks the transition from vegetative to aerial growth.
Keijser
Bart J F
BJ
Leiden Institute of Chemistry, Gorlaeus Laboratories, Leiden University, 2300 RA Leiden, The Netherlands.
van Wezel
Gilles P
GP
Canters
Gerard W
GW
Vijgenboom
Erik
E
D018528:ATP-Binding Cassette Transporters / Q000235:genetics; D000595:Amino Acid Sequence; D001426:Bacterial Proteins / Q000235:genetics*; D001483:Base Sequence; D004268:DNA-Binding Proteins; D015964:Gene Expression Regulation, Bacterial; D025301:Hyphae / Q000502:physiology; D008969:Molecular Sequence Data; D005810:Multigene Family; D009154:Mutation / Q000502:physiology; D009876:Operon / Q000235:genetics; D011401:Promoter Regions, Genetic / Q000235:genetics; D012329:RNA, Bacterial; D012356:RNA, Transfer, Leu / Q000235:genetics; D013302:Streptomyces / Q000235:genetics* / Q000254:growth & development; D014157:Transcription Factors; D014158:Transcription, Genetic / Q000235:genetics
D018528:ATP-Binding Cassette Transporters; D001426:Bacterial Proteins; C107344:BldA tRNA, Streptomyces coelicolor; C111307:BldB protein, Streptomyces coelicolor; C111306:BldD protein, Streptomyces coelicolor; D004268:DNA-Binding Proteins; D012329:RNA, Bacterial; D012356:RNA, Transfer, Leu; C087734:RamA protein, Streptomyces coelicolor; C087736:RamR protein, Streptomyces; D014157:Transcription Factors