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Journal of Bacteriology, January 2006, p. 677-686, Vol. 188, No. 2
0021-9193/06/$08.00+0 doi:10.1128/JB.188.2.677-686.2006
Copyright © 2006, American Society for Microbiology. All Rights Reserved.
Institut de Génétique et Microbiologie, Université Paris XI, 91405 Orsay, France,1 Institute of Molecular Biology, Dubravska cesta 21, 845 51 Bratislava, Slovak Republic2
Received 28 June 2005/ Accepted 16 September 2005
The PhoR/PhoP two-component system of Streptomyces lividans was previously shown to allow the growth of the bacteria at low Pi concentrations and to negatively control antibiotic production. The present study focuses on the transcriptional analysis of phoR and phoP, along with the phoU and mtpA genes that are transcribed divergently from the phoRP operon in S. lividans. The effect of phoR, phoP, phoU, and ppk mutations on transcription of these genes was examined under phosphate-replete and phosphate-limited conditions. We demonstrated that phoR and phoP were cotranscribed as a leaderless bicistronic transcript cleaved at discrete sites toward the 3' end of phoR. In addition, phoP could also be transcribed alone from a promoter located at the 3' end of phoR. The phoU and mtpA genes, predicted to encode metal binding proteins, were shown to be transcribed as monocistronic transcripts. The expression of phoR-phoP, phoP, and phoU was found to be induced under conditions of Pi limitation in S. lividans TK24. This induction, requiring both PhoR and PhoP, was significantly weaker in the phoU mutant but much stronger in the ppk mutant than in the parental strain. The expression of mtpA was also shown to be up-regulated when Pi was limiting but independently of PhoR/PhoP. The induction of mtpA expression was much stronger in the phoU mutant strain than in the other strains. This study revealed interesting regulatory interactions between the different genes and allowed us to propose putative roles for PhoU and MtpA in the adaptation to phosphate scarcity.
timent 400 de l'Université Paris 11, 91405 Orsay, France. Phone: 33 (0) 1 69 15 46 42. Fax: 33 (0) 1 69 15 45 44. E-mail: marie-joelle.virolle{at}igmors.u-psud.fr.
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