1. Heterocyst-specific expression of patB, a gene required for nitrogen fixation in Anabaena sp. strain PCC 7120.
- Author
-
Jones KM, Buikema WJ, and Haselkorn R
- Subjects
- Bacterial Proteins metabolism, Cell Division genetics, DNA-Binding Proteins metabolism, Electron Transport Complex IV genetics, Green Fluorescent Proteins, Helix-Turn-Helix Motifs, Luminescent Proteins genetics, Luminescent Proteins metabolism, Mutation, Operon, Phenotype, Promoter Regions, Genetic, Recombinant Proteins genetics, Recombinant Proteins metabolism, Transaminases metabolism, Anabaena physiology, Bacterial Proteins genetics, DNA-Binding Proteins genetics, Gene Expression Regulation, Bacterial, Genes, Bacterial, Nitrogen Fixation genetics, Nitrogen Fixation physiology, Transaminases genetics
- 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.
- Published
- 2003
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