Cross-talk between two global regulators in Streptomyces: PhoP and AfsR interact in the control of afsS, pstS and phoRP transcription

Authors

  • Fernando Santos-Beneit,

    1. Instituto de Biotecnología de León, INBIOTEC, Parque Científico de León, Avenue. Real, 1, 24006, León, Spain.
    Search for more papers by this author
  • Antonio Rodríguez-García,

    1. Instituto de Biotecnología de León, INBIOTEC, Parque Científico de León, Avenue. Real, 1, 24006, León, Spain.
    2. Área de Microbiología, Fac. CC. Biológicas y Ambientales, Universidad de León, Campus de Vegazana, s/n, 24071, León, Spain.
    Search for more papers by this author
  • Alberto Sola-Landa,

    1. Instituto de Biotecnología de León, INBIOTEC, Parque Científico de León, Avenue. Real, 1, 24006, León, Spain.
    Search for more papers by this author
  • Juan F. Martín

    Corresponding author
    1. Instituto de Biotecnología de León, INBIOTEC, Parque Científico de León, Avenue. Real, 1, 24006, León, Spain.
    2. Área de Microbiología, Fac. CC. Biológicas y Ambientales, Universidad de León, Campus de Vegazana, s/n, 24071, León, Spain.
    Search for more papers by this author

E-mail jf.martin@unileon.es; Tel. (+34) 987291 505/(+34) 987210 308; Fax (+34) 987291 506/(+34) 987210 388.

Summary

The regulatory proteins AfsR and PhoP control expression of the biosynthesis of actinorhodin and undecylprodigiosin in Streptomyces coelicolor. Electrophoretic mobility shift assays showed that PhoPDBD does not bind directly to the actII-ORF4, redD and atrA promoters, but it binds to the afsS promoter, in a region overlapping with the AfsR operator. DNase I footprinting studies revealed a PhoP protected region of 26 nt (PHO box; two direct repeats of 11 nt) that overlaps with the AfsR binding sequence. Binding experiments indicated a competition between AfsR and PhoP; increasing concentrations of PhoPDBD resulted in the disappearance of the AfsR–DNA complex. Expression studies using the reporter luxAB gene coupled to afsS promoter showed that PhoP downregulates afsS expression probably by a competition with the AfsR activator. Interestingly, AfsR binds to other PhoP-regulated promoters including those of pstS (a component of the phosphate transport system) and phoRP (encoding the two component system itself). Analysis of the AfsR-protected sequences in each of these promoters allowed us to distinguish the AfsR binding sequence from the overlapping PHO box. The reciprocal regulation of the phoRP promoter by AfsR and of afsS by PhoP suggests a fine interplay of these regulators on the control of secondary metabolism.

Ancillary