In:
Journal of Bacteriology, American Society for Microbiology, Vol. 187, No. 5 ( 2005-03), p. 1825-1832
Abstract:
Carotenoids are produced by a variety of organisms, but the mechanisms that regulate gene expression leading to carotenoid biosynthesis have been characterized for only a few organisms. In this study, we found that Streptomyces coelicolor A3(2), a gram-positive filamentous bacterium, produces carotenoids under blue light induction. The carotenoid fraction isolated from the cell extract contained multiple compounds, including isorenieratene and β-carotene. The carotenoid biosynthesis gene cluster of S. coelicolor consists of two convergent operons, crtEIBV and crtYTU , as previously shown for Streptomyces griseus . The crtEIBV null mutant completely lost its ability to produce carotenoids. The crt gene cluster is flanked by a regulatory region that consists of two divergent operons, litRQ and litSAB . The lit (light-induced transcription) genes encode a MerR-type transcriptional regulator (LitR), a possible oxidoreductase (LitQ), an extracytoplasmic function sigma factor (σ LitS ), a putative lipoprotein (LitA), and a putative anti-sigma factor (LitB). S1 protection assay revealed that the promoters preceding crtE (P crtE ), crtY (P crtY ), litR (P litR ), and litS (P litS ) are activated upon illumination. A litS mutant lost both the ability to produce carotenoids and the activities of P crtE , P crtY , and P litS , which suggested that σ LitS directs light-induced transcription from these promoters. An RNA polymerase holocomplex containing purified σ LitS recombinant protein generated specific P crtE and P crtY transcripts in an in vitro runoff transcriptional assay. A litR mutant that had an insertion of the kanamycin resistance gene was defective both in the ability to produce carotenoids and in all of the light-dependent promoter activities. Overexpression of litS resulted in constitutive carotenoid production in both the wild type and the litR mutant. These results indicate that σ LitS acts as a light-induced sigma factor that directs transcription of the crt biosynthesis gene cluster, whose activity is controlled by an unknown LitR function. This is the first report to describe light-inducible gene expression in Streptomyces .
Type of Medium:
Online Resource
ISSN:
0021-9193
,
1098-5530
DOI:
10.1128/JB.187.5.1825-1832.2005
Language:
English
Publisher:
American Society for Microbiology
Publication Date:
2005
detail.hit.zdb_id:
1481988-0
SSG:
12
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