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An alternative sigma factor governs the principal sigma factor in S treptomyces griseus
Author(s) -
Otani Hiroshi,
Higo Akiyoshi,
Nanamiya Hideaki,
Horinouchi Sueharu,
Ohnishi Yasuo
Publication year - 2013
Publication title -
molecular microbiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.857
H-Index - 247
eISSN - 1365-2958
pISSN - 0950-382X
DOI - 10.1111/mmi.12160
Subject(s) - sigma factor , biology , rna polymerase , streptomyces griseus , housekeeping gene , gene , genetics , mutant , transcription (linguistics) , gene expression , microbiology and biotechnology , rna , bacteria , streptomyces , linguistics , philosophy
Summary In bacteria, the RNA polymerase holoenzyme comprises a five‐subunit core enzyme and a dissociable subunit, sigma factor, which is responsible for transcriptional initiation. The filamentous bacterium S treptomyces griseus has 52 sigma factors, including one essential ‘principal’ sigma factor (σ HrdB ) that is responsible for the transcription of housekeeping genes. Here we characterized an alternative sigma factor (σ ShbA ), which is highly conserved within the genus S treptomyces . A σ ShbA ‐deficient mutant showed a severe growth defect and transcriptome analysis indicated that many housekeeping genes were downregulated in response to insufficient σ ShbA production. Biochemical and genetic analyses proved that σ ShbA is a major determinant of transcription of the σ HrdB gene. This observation of a principal sigma factor being governed by another sigma factor throughout growth is unprecedented. We found that increasing σ ShbA production with mycelial growth maintained a high σ HrdB level late in growth. Furthermore, a hrdB ‐autoregulatable σ ShbA ‐deficient mutant, in which the principal sigma factor gene can be transcribed by RNA polymerase containing σ HrdB itself, showed several defects: rapid mycelial lysis in stationary phase in liquid culture and delayed morphological development and impaired streptomycin production in solid culture. From these observations, we discuss the biological significance of control of σ HrdB by σ ShbA in S . griseus .