Affiliation:
1. Institut für Mikrobiologie und Molekularbiologie der Justus-Liebig-Universität Giessen, D-35392 Giessen
2. Lehrstuhl für Mikrobiologie der Universität München, D-80638 München
3. Abteilung für Mikrobiologie der Universität Osnabrück, D-49069 Osnabrück, Germany
Abstract
ABSTRACT
The transcription factor of the cyclic AMP receptor protein/FNR family, NtcA, and the P
II
signaling protein play central roles in global nitrogen control in cyanobacteria. A dependence on P
II
for NtcA-regulated transcription, however, has not been observed. In the present investigation, we examined alterations in gene expression following nitrogen deprivation in
Synechococcus elongatus
strain PCC 7942 and specifically the roles of NtcA and P
II
. Global changes in de novo protein synthesis following combined-nitrogen deprivation were visualized by in vivo [
35
S]methionine labeling and two-dimensional polyacrylamide gel electrophoresis analysis. Nearly all proteins whose synthesis responded specifically to combined-nitrogen deprivation in wild-type cells of
S. elongatus
failed to respond in P
II
- and NtcA-deficient mutants. One of the proteins whose synthesis was down-regulated in a P
II
- and NtcA-dependent manner was RbcS, the small subunit of RubisCO. Quantification of its mRNA revealed that the abundance of the
rbcLS
transcript following combined-nitrogen deprivation rapidly declined in wild-type cells but not in P
II
and NtcA mutant cells. To investigate further the relationship between P
II
and NtcA, fusions of the promotorless
luxAB
reporter genes to the NtcA-regulated
glnB
gene were constructed and these constructs were used to transform wild-type cells and P
II
−
and NtcA
−
mutants. Determination of bioluminescence under different growth conditions showed that NtcA represses gene expression in the presence of ammonium in a P
II
-independent manner. By contrast, NtcA-dependent activation of
glnB
expression following combined-nitrogen deprivation was impaired in the absence of P
II
. Together, these results suggest that under conditions of combined-nitrogen deprivation, the regulation of NtcA-dependent gene expression requires the P
II
signal transduction protein.
Publisher
American Society for Microbiology
Subject
Molecular Biology,Microbiology
Cited by
72 articles.
订阅此论文施引文献
订阅此论文施引文献,注册后可以免费订阅5篇论文的施引文献,订阅后可以查看论文全部施引文献