In:
Journal of Bacteriology, American Society for Microbiology, Vol. 186, No. 21 ( 2004-11), p. 7337-7343
Abstract:
Expression of the glnA gene encoding glutamine synthetase, a key enzyme in nitrogen metabolism, is subject to a variety of regulatory mechanisms in different organisms. In the filamentous, N 2 -fixing cyanobacterium Anabaena sp. strain PCC 7120, glnA is expressed from multiple promoters that generate several transcripts whose abundance is influenced by NtcA, the transcription factor exerting global nitrogen control in cyanobacteria. Whereas RNA I originates from a canonical NtcA-dependent promoter (P 1 ) and RNA II originates from a σ 70 -type promoter (P 2 ), RNA IV is influenced by NtcA but the corresponding promoter (P 3 ) does not have the structure of NtcA-activated promoters. Using RNA isolated from Anabaena filaments grown under different nitrogen regimens, we observed, in addition to these transcripts, RNA V , which has previously been detected only in in vitro transcription assays and should originate from P 4 . However, in heterocysts, which are differentiated cells specialized in N 2 fixation, RNA I was the almost exclusive glnA transcript. Analysis of P glnA :: lacZ fusions containing different fragments of the glnA upstream region confirmed that fragments carrying P 1 , P 2 , or P 3 and P 4 have the ability to promote transcription. Mutation of the NtcA-binding site in P 1 eliminated P 1 -directed transcription and allowed increased use of P 2 . The NtcA-binding site in the P 1 promoter and binding of NtcA to this site appear to be key factors in determining glnA gene expression in vegetative cells and heterocysts.
Type of Medium:
Online Resource
ISSN:
0021-9193
,
1098-5530
DOI:
10.1128/JB.186.21.7337-7343.2004
Language:
English
Publisher:
American Society for Microbiology
Publication Date:
2004
detail.hit.zdb_id:
1481988-0
SSG:
12
Bookmarklink