title: Identification of the oriC region and its influence on heterocyst development in the filamentous cyanobacterium Anabaena sp. strain PCC 7120.
abstract: Anabaena sp. strain PCC 7120 (Anabaena PCC 7120) is a filamentous, nitrogen-fixing cyanobacterium. Upon deprivation of combined nitrogen, about 5-10 % of the cells become heterocysts, i.e. cells devoted to N(2) fixation. Heterocysts are intercalated among vegetative cells and distributed in a semi-regular pattern, and adjacent heterocysts are rarely observed. Previously, we showed that the cell cycle could play a regulatory function during heterocyst development, although the mechanism involved remains unknown. As a further step to understand this phenomenon, we identified the oriC region for chromosomal DNA replication, located between dnaA and dnaN. The oriC region of Anabaena PCC 7120 was able to support the self-replication of a plasmid in the unicellular cyanobacterium Synechocystis sp. PCC 6803. Surprisingly, integration of the oriC region into the chromosome of Anabaena PCC 7120 through homologous recombination led to much slower cell growth in the absence of a combined-nitrogen source and to multiple contiguous proheterocysts after prolonged incubation. Real-time RT-PCR showed that expression of two heterocyst-related genes, hetR and hetN, was altered in these strains: hetR expression remained high 48 h after induction, and hetN increased to high levels after induction for 12 h. These results suggest that the balance between oriC and DnaA could be important for heterocyst development.
authors.affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, PR China.
authors.forename: Yin
authors.initials: Y
authors.lastname: Zhou
authors.affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, PR China.
authors.forename: Wen-Li
authors.initials: WL
authors.lastname: Chen
authors.affiliation: State Key Laboratory of Agricultural Microbiology, Huazhong Agricultural University, Wuhan 430070, PR China.
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.affiliation: Aix-Marseille Université and Laboratoire de Chimie Bactérienne, CNRS-UPR9043, 31, chemin Joseph Aiguier, 13402 Marseille cedex 20, France.
authors.forename: Cheng-Cai
authors.initials: CC
authors.lastname: Zhang
mesh_terms: D017033:Anabaena / Q000235:genetics* / Q000254:growth & development* / Q000378:metabolism; D001426:Bacterial Proteins / Q000096:biosynthesis / Q000235:genetics / Q000378:metabolism; D015139:Blotting, Southern; D002453:Cell Cycle; D004268:DNA-Binding Proteins / Q000235:genetics; D004259:DNA-Directed DNA Polymerase / Q000235:genetics; D020440:Gene Duplication / Q000235:genetics*; D015964:Gene Expression Regulation, Bacterial; D009586:Nitrogen Fixation / Q000235:genetics*; D051738:Origin Recognition Complex / Q000235:genetics*; D010088:Oxidoreductases / Q000096:biosynthesis; D010957:Plasmids; D016133:Polymerase Chain Reaction
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; C066312:DnaA protein, Bacteria; C114650:OriC chromosomal replication origin; D051738:Origin Recognition Complex; C067403:HetR protein, Bacteria; D010088:Oxidoreductases; C107239:HetN protein, Anabaena; D004259:DNA-Directed DNA Polymerase; C083980:dnaN protein, Bacteria