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FurA is the master regulator of iron homeostasis and modulates the expression of tetrapyrrole biosynthesis genes in Anabaena sp. PCC 7120

Authors

  • Andrés González,

    1. Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, Spain
    2. Instituto de Biocomputación y Física de Sistemas Complejos (BIFI), Universidad de Zaragoza, Zaragoza, Spain
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  • M. Teresa Bes,

    1. Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, Spain
    2. Instituto de Biocomputación y Física de Sistemas Complejos (BIFI), Universidad de Zaragoza, Zaragoza, Spain
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  • Ana Valladares,

    1. Instituto de Bioquímica Vegetal y Fotosíntesis, Centro de Investigaciones Científicas Isla de la Cartuja, CSIC-Universidad de Sevilla, Seville, Spain
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  • M. Luisa Peleato,

    1. Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, Spain
    2. Instituto de Biocomputación y Física de Sistemas Complejos (BIFI), Universidad de Zaragoza, Zaragoza, Spain
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  • María F. Fillat

    Corresponding author
    1. Instituto de Biocomputación y Física de Sistemas Complejos (BIFI), Universidad de Zaragoza, Zaragoza, Spain
    • Departamento de Bioquímica y Biología Molecular y Celular, Universidad de Zaragoza, Zaragoza, Spain
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For correspondence. E-mail fillat@unizar.es; Tel. (+34) 976 76 1282; Fax (+34) 976 76 2123.

Summary

Knowledge on the regulatory mechanisms controlling iron homeostasis in cyanobacteria is limited. In Anabaena sp. PCC 7120, the ferric uptake regulator FurA is a constitutive and essential protein whose expression is induced under iron deprivation. Our previous analyses have shown that this protein acts as a global transcriptional regulator, controlling the expression of several genes belonging to different functional categories, including schT, a gene coding for a TonB-dependent schizokinen transporter. In the present study we analysed the impact of FurA overexpression and iron availability on the transcriptional modulation of a broad range of Anabaena iron uptake, transport, storage and cellular iron utilization mechanisms, including enzymes involved in siderophore biosynthesis, TonB-dependent siderophore outer membrane transporters, siderophore periplasmic binding proteins, ABC inner membrane permeases, ferritin Dps family proteins, and enzymes involved in tetrapyrrole biosynthesis. By combining reverse transcription-PCR analyses, electrophoretic mobility shift assays and DNase I footprinting experiments, we defined a variety of novel direct iron-dependent transcriptional targets of this metalloregulator, including genes encoding at least five enzymes involved in the tetrapyrrole biosynthesis pathway. The results unravel the role of FurA as the master regulator of iron homeostasis in Anabaena sp. PCC 7120, providing new insights into the Fur regulons in cyanobacteria.

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