title: Importance and regulation of inositol biosynthesis during growth and differentiation of Streptomyces.
abstract: Unusually among bacteria, actinobacteria possess myo-inositol 1-phosphate synthase (mIPS). In the developmentally complex Streptomyces coelicolor, the mIPS-encoding gene (inoA) is cotranscribed with a putative regulatory gene (inoR). The inoRA transcript was more abundant in an inoR in-frame deletion mutant, and InoR formed different complexes in vitro with an extensive region around the inoRA promoter. Binding was relieved by adding glucose 6-phosphate. Thus, InoR is a metabolite-sensitive autorepressor that influences inoA expression, and hence the level of inositol, by controlling transcription from P(inoRA) . Disruption of inoA resulted in inositol-dependent growth and development, with full phenotypic correction at 0.1 mM inositol: at lower inositol concentrations differentiation was arrested at intermediate stages. This pattern may partly reflect increased demand for membrane phospholipids during sporulation septation. A corresponding sharp upregulation of inoRA transcription coincident with sporulation was dependent on a developmental regulator, WhiI. A truncated form of WhiI could bind two sites downstream of P(inoRA) , and one of the WhiI-binding sites overlapped the InoR-binding site. The combined action of a metabolic regulator and a developmental regulator at the simple P(inoRA) promoter is a previously undescribed strategy for the differential provision of developmentally appropriate levels of a substance required during the formation of spore chains.
authors.affiliation: State Key Laboratory of Microbial Resources, Institute of Microbiology, Chinese Academy of Sciences, Beijing 100101, China.
authors.forename: Guohua
authors.initials: G
authors.lastname: Zhang
authors.forename: Yuqing
authors.initials: Y
authors.lastname: Tian
authors.forename: Kun
authors.initials: K
authors.lastname: Hu
authors.forename: Yu
authors.initials: Y
authors.lastname: Zhu
authors.forename: Keith F
authors.initials: KF
authors.lastname: Chater
authors.forename: Chi
authors.initials: C
authors.lastname: Feng
authors.forename: Gang
authors.initials: G
authors.lastname: Liu
authors.forename: Huarong
authors.initials: H
authors.lastname: Tan
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial; D007294:Inositol / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D007296:Myo-Inositol-1-Phosphate Synthase / Q000235:genetics / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D013171:Spores, Bacterial / Q000201:enzymology / Q000235:genetics / Q000254:growth & development / Q000378:metabolism; D048372:Streptomyces coelicolor / Q000201:enzymology / Q000235:genetics / Q000254:growth & development* / Q000378:metabolism*
chemical_list: D001426:Bacterial Proteins; D007294:Inositol; D007296:Myo-Inositol-1-Phosphate Synthase