title: CmpR is important for circadian phasing and cell growth.
abstract: In the cyanobacterium Synechococcus elongatus PCC 7942, the circadian clock entrains to a daily light/dark cycle. The transcription factor Pex is abundant under dark conditions and represses kaiA transcription to fine-tune the KaiC-based core circadian oscillator. The transcription of pex also increases during exposure to darkness; however, its mechanism is unknown. We performed a molecular genetic study by constructing a pex expression bioluminescent reporter and screening for brightly luminescent mutants by random insertion of a drug resistance gene cassette in the reporter genome. One mutant contained an insertion of an antibiotic resistance cassette in the cmpR locus, a transcriptional regulator of inorganic carbon concentration. Insertions of the cassette in the remaining two mutant genomes were in the genes encoding flavodoxin and a putative partner of an ABC transporter with unknown function (ycf22). We further analyzed the cmpR mutant to examine whether CmpR directly or indirectly targeted pex expression. In the cmpR mutant, the pex mRNA level was 1.8-fold that of the wild type, and its circadian peak phase in bioluminescence rhythm occurred 5 h later. Moreover, a high-light stress phenotype was present in the colony. The abnormalities were complemented by ectopic induction of the native gene. However, the cmpR/pex double mutation partly suppressed the phase abnormality (2.5 h). In vitro DNA binding analysis of CmpR showed positive binding to the psbAII promoter, but not to any pex DNA. We postulate that the phenotypes of cmpR-deficient cells were attributable mainly to a feeble metabolic and/or redox status.
authors: Department of Genome System Science, Graduate School of Nanobioscience, Yokohama City University, Seto 22-2, Kanazawa-ku, Yokohama 236-0027, Japan.
authors: Hiromitsu
authors: H
authors: Tanaka
authors: Mai
authors: M
authors: Kitamura
authors: Yoko
authors: Y
authors: Nakano
authors: Mitsunori
authors: M
authors: Katayama
authors: Yukari
authors: Y
authors: Takahashi
authors: Takao
authors: T
authors: Kondo
authors: Katsushi
authors: K
authors: Manabe
authors: Tatsuo
authors: T
authors: Omata
authors: Shinsuke
authors: S
authors: Kutsuna
mesh_terms: D001426:Bacterial Proteins / Q000378:metabolism*; D001483:Base Sequence; D049109:Cell Proliferation / Q000528:radiation effects; D002940:Circadian Rhythm / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects; D004269:DNA, Bacterial / Q000235:genetics / Q000378:metabolism; D004268:DNA-Binding Proteins / Q000378:metabolism*; D015964:Gene Expression Regulation, Bacterial / Q000528:radiation effects; D005798:Genes, Bacterial / Q000235:genetics; D017930:Genes, Reporter; D005816:Genetic Complementation Test; D008027:Light; D008164:Luminescent Proteins / Q000378:metabolism; D008954:Models, Biological; D008969:Molecular Sequence Data; D009154:Mutation / Q000235:genetics; D010641:Phenotype; D011401:Promoter Regions, Genetic / Q000235:genetics; D011485:Protein Binding / Q000528:radiation effects; D012333:RNA, Messenger / Q000235:genetics / Q000378:metabolism; D013489:Suppression, Genetic / Q000528:radiation effects; D046940:Synechococcus / Q000166:cytology* / Q000235:genetics / Q000502:physiology* / Q000528:radiation effects
chemical_list: D001426:Bacterial Proteins; D004269:DNA, Bacterial; D004268:DNA-Binding Proteins; D008164:Luminescent Proteins; D012333:RNA, Messenger; C422911:cmpR protein, Synechococcus