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Journal of Bacteriology, November 1999, p. 6664-6669, Vol. 181, No. 21
Instituto de Bioquímica Vegetal y
Fotosíntesis, Consejo Superior de Investigaciones
Científicas-Universidad de Sevilla, Centro de Investigaciones
Científicas Isla de la Cartuja, E-41092 Seville, Spain
Received 14 June 1999/Accepted 18 August 1999
The heterocyst is the site of nitrogen fixation in aerobically
grown cultures of some filamentous cyanobacteria. Heterocyst development in Anabaena sp. strain PCC 7120 is dependent on
the global nitrogen regulator NtcA and requires, among others, the products of the hetR and hetC genes. Expression
of hetC, tested by RNA- DNA hybridization, was impaired in
an ntcA mutant. A nitrogen-regulated, NtcA-dependent
putative transcription start point was localized at nucleotide
0021-9193/99/$04.00+0
Copyright © 1999, American Society for Microbiology. All rights reserved.
The hetC Gene Is a Direct Target of the
NtcA Transcriptional Regulator in Cyanobacterial Heterocyst
Development
571
with respect to the hetC translational start. Sequences
upstream from this transcription start point exhibit the structure of
the canonical cyanobacterial promoter activated by NtcA, and purified
NtcA protein specifically bound to a DNA fragment containing this
promoter. Activation of expression of hetC during
heterocyst development appears thus to be directly operated by NtcA.
NtcA-mediated activation of hetR expression was not
impaired in a hetC mutant, indicating that HetC is not an
NtcA-dependent element required for hetR induction.
*
Corresponding author. Mailing address: Instituto de
Bioquímica Vegetal y Fotosíntesis, Consejo Superior de
Investigaciones Científicas-Universidad de Sevilla, Centro de
Investigaciones Científicas Isla de la Cartuja, Avda.
Américo Vespucio s/n, E-41092 Seville, Spain. Phone:
34-95-4489522. Fax: 34-95-4460065. E-mail: herrero{at}cica.es.
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