title: Efficient Gene Induction and Endogenous Gene Repression Systems for the Filamentous Cyanobacterium Anabaena sp. PCC 7120.
abstract: In the last decade, many studies have been conducted to employ genetically engineered cyanobacteria in the production of various metabolites. However, the lack of a strict gene regulation system in cyanobacteria has hampered these attempts. The filamentous cyanobacterium Anabaena sp. PCC 7120 performs both nitrogen and carbon fixation and is, therefore, a good candidate organism for such production. To employ Anabaena cells for this purpose, we intended to develop artificial gene regulation systems to alter the cell metabolic pathways efficiently. We introduced into Anabaena a transcriptional repressor TetR, widely used in diverse organisms, and green fluorescent protein (GFP) as a reporter. We found that anhydrotetracycline (aTc) substantially induced GFP fluorescence in a concentration-dependent manner. By expressing tetR under the nitrate-specific promoter nirA, we successfully reduced the concentration of aTc required for the induction of gfp under nitrogen fixation conditions (to 10% of the concentration needed under nitrate-replete conditions). Further, we succeeded in the overexpression of GFP by depletion of nitrate without the inducer by means of promoter engineering of the nirA promoter. Moreover, we applied these gene regulation systems to a metabolic enzyme in Anabaena and successfully repressed glnA, the gene encoding glutamine synthetase that is essential for nitrogen assimilation in cyanobacteria, by expressing the small antisense RNA for glnA. Consequently, the ammonium production of an ammonium-excreting Anabaena mutant was significantly enhanced. We therefore conclude that the gene regulation systems developed in this study are useful tools for the regulation of metabolic enzymes and will help to increase the production of desired substances in Anabaena.
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta 4259-R1-8, Midori-ku, Yokohama, 226-8503 Japan Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Tokyo, 102-0075 Japan.
authors.forename: Akiyoshi
authors.initials: A
authors.lastname: Higo
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta 4259-R1-8, Midori-ku, Yokohama, 226-8503 Japan Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Tokyo, 102-0075 Japan.
authors.forename: Atsuko
authors.initials: A
authors.lastname: Isu
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta 4259-R1-8, Midori-ku, Yokohama, 226-8503 Japan Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Tokyo, 102-0075 Japan.
authors.forename: Yuki
authors.initials: Y
authors.lastname: Fukaya
authors.affiliation: Chemical Resources Laboratory, Tokyo Institute of Technology, Nagatsuta 4259-R1-8, Midori-ku, Yokohama, 226-8503 Japan Core Research for Evolutional Science and Technology (CREST), Japan Science and Technology Agency (JST), Tokyo, 102-0075 Japan thisabor@res.titech.ac.jp.
authors.forename: Toru
authors.initials: T
authors.lastname: Hisabori
mesh_terms: D000641:Ammonia / Q000378:metabolism; D017033:Anabaena / Q000235:genetics* / Q000254:growth & development; D001483:Base Sequence; D015964:Gene Expression Regulation, Bacterial; D005818:Genetic Engineering; D049452:Green Fluorescent Proteins / Q000378:metabolism; D008969:Molecular Sequence Data; D011401:Promoter Regions, Genetic; D013997:Time Factors
chemical_list: D049452:Green Fluorescent Proteins; D000641:Ammonia
keywords: Biotechnology; Cyanobacteria; Gene regulation; Metabolic engineering; Small RNA