title: Heterocyst-specific expression of patB, a gene required for nitrogen fixation in Anabaena sp. strain PCC 7120.
abstract: The patB gene product is required for growth and survival of the filamentous cyanobacterium Anabaena sp. strain PCC 7120 in the absence of combined nitrogen. A patB::gfp fusion demonstrated that this gene is expressed exclusively in heterocysts. patB mutants have a normal initial pattern of heterocyst spacing along the filament but differentiate excess heterocysts after several days in the absence of combined nitrogen. Expression of hetR and patS, two critical regulators of the heterocyst development cascade, are normal for patB mutants, indicating that patB acts downstream of them in the differentiation pathway. A patB deletion mutant suffers an almost complete cessation of growth and nitrogen fixation within 24 h of combined nitrogen removal. In contrast, a new PatB mutant that is defective in its N-terminal ferredoxin domain, or a previously described mutant that has a frameshift removing its C-terminal helix-turn-helix domain, grows very slowly and differentiates multiple contiguous heterocysts under nitrogen-deficient conditions.
authors.affiliation: Department of Molecular Genetics and Cell Biology, University of Chicago, Chicago, Illinois 60637, USA.
authors.forename: Kathryn M
authors.initials: KM
authors.lastname: Jones
authors.forename: William J
authors.initials: WJ
authors.lastname: Buikema
authors.forename: Robert
authors.initials: R
authors.lastname: Haselkorn
mesh_terms: D017033:Anabaena / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics* / Q000378:metabolism; D002455:Cell Division / Q000235:genetics; D004268:DNA-Binding Proteins / Q000235:genetics* / Q000378:metabolism; D003576:Electron Transport Complex IV / Q000235:genetics; D015964:Gene Expression Regulation, Bacterial; D005798:Genes, Bacterial; D049452:Green Fluorescent Proteins; D019077:Helix-Turn-Helix Motifs; D008164:Luminescent Proteins / Q000235:genetics / Q000378:metabolism; D009154:Mutation; D009586:Nitrogen Fixation / Q000235:genetics / Q000502:physiology*; D009876:Operon; D010641:Phenotype; D011401:Promoter Regions, Genetic; D011994:Recombinant Proteins / Q000235:genetics / Q000378:metabolism; D000637:Transaminases / Q000235:genetics* / Q000378:metabolism
chemical_list: D001426:Bacterial Proteins; D004268:DNA-Binding Proteins; D008164:Luminescent Proteins; C115380:PatS protein, Anabaena; D011994:Recombinant Proteins; C067403:HetR protein, Bacteria; D049452:Green Fluorescent Proteins; D003576:Electron Transport Complex IV; C080236:PatB protein, Nostoc sp. PCC 7120; D000637:Transaminases