title: Evidence for the negative regulation of phytase gene expression in Streptomyces lividans and Streptomyces coelicolor.
abstract: Sco7697, a gene encoding a phytase, enzyme able to degrade phytate (myo-inositol 1,2,3,4,5,6-hexakis phosphate), the most abundant phosphorus storing compound in plants is present in the genome of S. coelicolor, a soil born bacteria with a saprophytic lifestyle. The expression of this gene was previously shown to be induced in conditions of Pi limitation by the response regulator PhoP binding to an operator sequence, the PHO box, located upstream of the -35 promoter sequence. A close examination of the promoter region of sco7697 revealed the presence of another putative operator site, a Direct Repeat (DR), located downstream of the -10 promoter sequence. In order to determine whether this DR played a role in regulation of sco7697 expression, different variants of the phytase gene promoter region were transcriptionally fused to the ß-glucuronidase reporter gene (GUS). As expected, deletion of the PHO box led to abolition of sco7697 induction in conditions of Pi limitation. Interestingly, alteration of the DR correlated with a dramatic increase of GUS expression but only when PhoP was present. These results demonstrated that this DR is the site of strong negative regulation by an unknown repressor. The latter would impede the necessary activation of phytase expression by PhoP.
authors.affiliation: Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, University Paris-Sud, Orsay, France.|Laboratory of Microorganisms and Biomolecules, Centre of Biotechnology of Sfax, University of Sfax, Sfax, Tunisia.
authors.forename: Ines
authors.initials: I
authors.lastname: Boukhris
authors.affiliation: Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, University Paris-Sud, Orsay, France.
authors.forename: Thierry
authors.initials: T
authors.lastname: Dulermo
authors.affiliation: Laboratory of Microorganisms and Biomolecules, Centre of Biotechnology of Sfax, University of Sfax, Sfax, Tunisia.
authors.forename: Hichem
authors.initials: H
authors.lastname: Chouayekh
authors.affiliation: Institute for Integrative Biology of the Cell (I2BC), CEA, CNRS, University Paris-Sud, Orsay, France.
authors.forename: Marie-Joëlle
authors.initials: MJ
authors.lastname: Virolle
mesh_terms: D010832:6-Phytase / Q000096:biosynthesis / Q000235:genetics* / Q000378:metabolism; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial; D005966:Glucuronidase / Q000235:genetics; D009876:Operon; D010833:Phytic Acid / Q000378:metabolism; D011401:Promoter Regions, Genetic; D011485:Protein Binding; D012091:Repetitive Sequences, Nucleic Acid; D017384:Sequence Deletion; D012988:Soil Microbiology; D048372:Streptomyces coelicolor / Q000201:enzymology / Q000235:genetics*; D048170:Streptomyces lividans / Q000201:enzymology / Q000235:genetics*
chemical_list: D001426:Bacterial Proteins; D010833:Phytic Acid; D010832:6-Phytase; D005966:Glucuronidase
keywords: Beta-glucuronidase reporter gene; Negative; PHO box; PhoP; PhoR; Phosphate limitation; Positive regulation; Streptomyces phytase