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Journal of Bacteriology, December 2006, p. 8520-8525, Vol. 188, No. 24
0021-9193/06/$08.00+0     doi:10.1128/JB.01314-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.

NrrA Directly Regulates Expression of hetR during Heterocyst Differentiation in the Cyanobacterium Anabaena sp. Strain PCC 7120{triangledown}

Shigeki Ehira1 and Masayuki Ohmori1,2*

Department of Biochemistry and Molecular Biology, Faculty of Science, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570, Japan,1 Center of Systems Biology and Ecology, Faculty of Science, Toho University, 2-2-1 Miyama, Funabashi, Chiba 274-8510, Japan2

Received 18 August 2006/ Accepted 4 October 2006

Heterocyst differentiation in the cyanobacterium Anabaena sp. strain PCC 7120 requires NtcA, the global nitrogen regulator in cyanobacteria, and HetR, the master regulator of heterocyst differentiation. Expression of hetR is upregulated by nitrogen deprivation, and its upregulation depends on NtcA. However, it has not yet been revealed how NtcA regulates the expression of hetR. In the experiments presented here, it was confirmed that NrrA (All4312), a nitrogen-responsive response regulator, was required for the upregulation of hetR. The use of the nitrogen-responsive transcription initiation sites (TISs) for the hetR gene depended upon NrrA. NrrA bound specifically to the region upstream of TISs located at positions –728 and –696 in vitro. Overexpression of nrrA resulted in enhanced hetR expression and heterocyst formation. A molecular regulatory cascade is proposed whereby NtcA upregulates the expression of nrrA upon limitation of combined nitrogen in the medium and then NrrA upregulates the expression of hetR, leading to heterocyst differentiation.

* Corresponding author. Mailing address: Department of Biochemistry and Molecular Biology, Faculty of Science, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570, Japan. Phone: 81-48-858-3402. Fax: 81-48-858-3384. E-mail: ohmori{at}molbiol.saitama-u.ac.jp.

{triangledown} Published ahead of print on 13 October 2006.

Journal of Bacteriology, December 2006, p. 8520-8525, Vol. 188, No. 24
0021-9193/06/$08.00+0     doi:10.1128/JB.01314-06
Copyright © 2006, American Society for Microbiology. All Rights Reserved.



This article has been cited by other articles:

  • Jang, J., Shi, L., Tan, H., Janicki, A., Zhang, C.-C. (2009). Mutual Regulation of ntcA and hetR during Heterocyst Differentiation Requires Two Similar PP2C-Type Protein Phosphatases, PrpJ1 and PrpJ2, in Anabaena sp. Strain PCC 7120. J. Bacteriol. 191: 6059-6066 [Abstract] [Full Text]  
  • Muro-Pastor, A. M., Flores, E., Herrero, A. (2009). NtcA-Regulated Heterocyst Differentiation Genes hetC and devB from Anabaena sp. Strain PCC 7120 Exhibit a Similar Tandem Promoter Arrangement. J. Bacteriol. 191: 5765-5774 [Abstract] [Full Text]  
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