title: [ECF-σ5 in Sreptomyces avermitilis is involved in regulation of avermectin biosynthesis and stress response].
abstract: OBJECTIVE
  We investegated the role of extracytoplasmic function (ECF) σ factor, σ5, in avermectin biosynthesis, morphological differentiation and stress response in S. avermitilis.
  
  
  METHODS
  We constructed sig5 gene deletion, complementation and overexpression strains and determined the role of σ5 in avermectin production and morphological differentiation by shaking flask fermentation and morphological observation of these strains. We used RT-qPCR, EMSA and ChIP assays to identify the target genes of σ5. We used stress tests to reveal the stress response that σ5 may be involved in.
  
  
  RESULTS
  Determination of avermectin production and morphological observation in sig5 related strains implied that σ5 inhibits avermectin production, but has no effect on growth or morphology. Deletion of sig5 increased transcription levels of pathway-specific activator gene aveR and structural gene aveAl, but σ5 did not bind to the promoter regions of aveR and aveAl. RT-qPCR and ChIP assays showed that σ5 positively regulates the transcription of itself and adjacent genes by binding to the promoter regions of sig5, SA V612, SA V615 and SA V618. Stress tests suggested that σ5 is involved in responding to osmotic stress.
  
  
  CONCLUSIONS
  Our findings indicated that σ5 indirectly inhibits avermectin production by affecting transcription of ave genes.
authors.forename: Shuai
authors.initials: S
authors.lastname: Luo
authors.forename: Di
authors.initials: D
authors.lastname: Sun
authors.forename: Zhi
authors.initials: Z
authors.lastname: Chen
authors.forename: Ying
authors.initials: Y
authors.lastname: Wen
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D015536:Down-Regulation; D015964:Gene Expression Regulation, Bacterial; D007559:Ivermectin / Q000031:analogs & derivatives* / Q000378:metabolism; D011401:Promoter Regions, Genetic; D012808:Sigma Factor / Q000235:genetics / Q000378:metabolism*; D013302:Streptomyces / Q000235:genetics / Q000254:growth & development / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D012808:Sigma Factor; D007559:Ivermectin; C019264:avermectin