Regulated expression of glutamyl-tRNA synthetase is directed by a mobile genetic element in the cyanobacterium Tolypothrix sp. PCC 7601

Authors

  • Ignacio Luque,

    Corresponding author
    1. Dpto Fisiología, Genética y Microbiología, Facultad de Ciencias, Universidad de Alicante, Campus de San Vicente, Alicante 03080, Spain.
    2. Organismes Photosynthétiques et Environnement. UMR8541, CNRS/Ecole Normale Supérieure, 46 rue d’Ulm, 75230 Paris Cedex 05, France.
    3. Unité des Cyanobactéries (CNRS-URA2172), Institut Pasteur, 28 rue du Dr Roux F-75724 Paris Cedex 15, France.
    Search for more papers by this author
  • Alfonso Andújar,

    1. Dpto Fisiología, Genética y Microbiología, Facultad de Ciencias, Universidad de Alicante, Campus de San Vicente, Alicante 03080, Spain.
    Search for more papers by this author
  • Lin Jia,

    1. Unité des Cyanobactéries (CNRS-URA2172), Institut Pasteur, 28 rue du Dr Roux F-75724 Paris Cedex 15, France.
    Search for more papers by this author
  • Gérald Zabulon,

    1. Organismes Photosynthétiques et Environnement. UMR8541, CNRS/Ecole Normale Supérieure, 46 rue d’Ulm, 75230 Paris Cedex 05, France.
    Search for more papers by this author
  • Nicole Tandeau De Marsac,

    1. Unité des Cyanobactéries (CNRS-URA2172), Institut Pasteur, 28 rue du Dr Roux F-75724 Paris Cedex 15, France.
    Search for more papers by this author
  • Enrique Flores,

    1. Intituto de Bioquímica Vegetal y Fotosíntesis. C.S.I.C.-Universidad de Sevilla, Avda Américo Vespucio 49, E-41092 Sevilla, Spain.
    Search for more papers by this author
  • Jean Houmard

    1. Organismes Photosynthétiques et Environnement. UMR8541, CNRS/Ecole Normale Supérieure, 46 rue d’Ulm, 75230 Paris Cedex 05, France.
    2. Unité des Cyanobactéries (CNRS-URA2172), Institut Pasteur, 28 rue du Dr Roux F-75724 Paris Cedex 15, France.
    Search for more papers by this author

*E-mail ignacio.luque@ua.es; Tel. (+34) 965 909 719; Fax (+34) 965 909 569.

Summary

The genome of Tolypothrix sp. PCC 7601 carries two copies of a novel insertion sequence, ISTosp1. One of the two copies is located upstream of the gene encoding glutamyl-tRNA synthetase, an enzyme playing a key role in protein and pigment synthesis. The tnpA gene of the IS element and gltX were co-transcribed and their expression was transiently upregulated upon retrieval of the ammonium source irrespective of whether nitrate or no nitrogen source were available. The second copy is also transcribed and shows a similar regulatory pattern. Structural elements of the promoter (−10 and −35 sequences) directing the expression of the tnpA-gltX operon have been localized within the IS. Regulatory sequences involving the NtcA transcription factor in the control of tnpA-gltX expression were found both within and in sequences upstream of the insertion element. The expression of gltX in a closely related cyanobacterium, Nostoc sp. PCC 7120, which lacks the insertion upstream of gltX, decreased upon ammonium retrieval, a regulatory pattern that markedly differs from that observed in Tolypothrix sp. PCC 7601. ISTosp1 constitutes a good example of how cells can make use of a transposable element to evolve an original regulatory mechanism.

Ancillary