Importance and regulation of inositol biosynthesis during growth and differentiation of Streptomyces

Abstract

SummaryUnusually 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 InoRbinding site. The combined action of a metabolic regulator and a developmental regulator at the simple PinoRA promoter is a previously undescribed strategy for the differential provision of developmentally appropriate levels of a substance required during the formation of spore chains.

Formations of Hydroxyapatite and Inositol Hexakisphosphate in Poultry Litter during the Composting Period: Sequential Fractionation, P K-edge XANES and Solution 31P NMR Investigations

“…Some thermophillic actinobacteria occurring frequently in the high-temperature compost are known to possess the precursor compounds for IHP (i.e., inositol and phosphatidylinositol),31,32 which may contribute to the formation of IHP and P o compounds in our samples. A relatively high concentration of H 2 O-P (39% of total P in K0,…”

Response Regulator Heterodimer Formation Controls a Key Stage in Streptomyces Development

“…In a recent study, evidence was presented that the DNA-binding domain of S. coelicolor WhiI (in the absence of the receiver domain) can bind in vitro to the promoter of the sco3900-sco3899 operon encoding a transcriptional regulator (InoR) and an inositol 1-phosphate synthase (InoA), respectively [43]. Our ChIP-Seq data show that WhiI does not regulate these genes in S. venezuelae .…”

Recent advances in understanding Streptomyces

“…Although whiG transcription depends on WhiA and WhiB in S. venezuelae 71 , in S. coelicolor its transcription was nearly the same in whiA or whiB mutants as in the wild-type 76 . In another example, the promoter of the WhiI-dependent inoA gene of S. coelicolor (for inositol phosphate synthetase) could bind truncated WhiI in vitro 77 , indicating that WhiI could bind DNA in the absence of BldM; yet in ChIP-seq analysis of an S. venezuelae bldM mutant, WhiI did not bind to any targets 70 . Other inter-species differences were previously noted between S. coelicolor and S. griseus 78 .…”