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Journal of Bacteriology, July 2006, p. 4822-4829, Vol. 188, No. 13
0021-9193/06/$08.00+0     doi:10.1128/JB.00258-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

A Pair of Iron-Responsive Genes Encoding Protein Kinases with a Ser/Thr Kinase Domain and a His Kinase Domain Are Regulated by NtcA in the Cyanobacterium Anabaena sp. Strain PCC 7120

Yong Cheng,1 Jian-Hong Li,2,3 Lei Shi,1 Li Wang,1 Amel Latifi,2 and Cheng-Cai Zhang1,2*

National Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, People's Republic of China,1 Laboratoire de Chimie Bactérienne, UPR9043, IBSM-CNRS, 31 Chemin Joseph Aiguier, 13402 Marseille cedex 20, France,2 Jiangsu Provincial Key Laboratory of Biodiversity and Biotechnology, Nanjing Normal University, Nanjing 210097, People's Republic of China3

Received 19 February 2006/ Accepted 24 April 2006

The filamentous cyanobacterium Anabaena sp. strain PCC 7120 can fix N2 when combined nitrogen is not available in the growth medium. It has a family of 13 genes encoding proteins with both a Ser/Thr kinase domain and a His kinase domain. The function of these enzymes is unknown. Two of them are encoded by pkn41 (alr0709) and pkn42 (alr0710). These two genes are separated by only 72 bp on the chromosome, and our results indicate that they are cotranscribed. The expression of pkn41 and pkn42 is induced by iron deprivation irrespective of the nature of the nitrogen source. Mutants inactivating either pkn41, pkn42, or both grow similarly to the wild type under normal conditions, but their growth is impaired either in the presence of an iron chelator or under conditions of nitrogen fixation and iron limitation, two situations where the demand for iron is particularly strong. Consistent with these results, these mutants display lower iron content than the wild type and a higher level of expression for nifJ1 and nifJ2, which encode pyruvate:ferredoxin oxidoreductases. Both nifJ1 and nifJ2 are known to be induced by iron limitation. NtcA, a global regulatory factor for different metabolic pathways, binds to the putative promoter region of pkn41, and the induction of pkn41 in response to iron limitation no longer occurs in an ntcA mutant. Our results suggest that ntcA not only regulates the expression of genes involved in nitrogen and carbon metabolism but also coordinates iron acquisition and nitrogen metabolism by activating the expression of pkn41 and pkn42.

* Corresponding author. Mailing address: Laboratoire de Chimie Bactérienne, 31 chemin J. Aiguier, 13402 Marseille cedex 20, France. Phone: 33 4 91164096. Fax: 33 4 91718914. E-mail: cczhang{at}ibsm.cnrs-mrs.fr.

Journal of Bacteriology, July 2006, p. 4822-4829, Vol. 188, No. 13
0021-9193/06/$08.00+0     doi:10.1128/JB.00258-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



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  • Lopez-Gomollon, S., Hernandez, J. A., Wolk, C. P., Peleato, M. L., Fillat, M. F. (2007). Expression of furA is modulated by NtcA and strongly enhanced in heterocysts of Anabaena sp. PCC 7120. Microbiology 153: 42-50 [Abstract] [Full Text]  


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