title: Global gene expression patterns of Nostoc punctiforme in steady-state dinitrogen-grown heterocyst-containing cultures and at single time points during the differentiation of akinetes and hormogonia.
abstract: The vegetative cells of the filamentous cyanobacterium Nostoc punctiforme can differentiate into three mutually exclusive cell types: nitrogen-fixing heterocysts, spore-like akinetes, and motile hormogomium filaments. A DNA microarray consisting of 6,893 N. punctiforme genes was used to identify the global transcription patterns at single time points in the three developmental states, compared to those in ammonium-grown time zero cultures. Analysis of ammonium-grown cultures yielded a transcriptome of 2,935 genes, which is nearly twice the size of a soluble proteome. The NH(4)(+)-grown transcriptome was enriched in genes encoding core metabolic functions. A steady-state N(2)-grown (heterocyst-containing) culture showed differential transcription of 495 genes, 373 of which were up-regulated. The majority of the up-regulated genes were predicted from studies of heterocyst differentiation and N(2) fixation; other genes are candidates for more detailed genetic analysis. Three days into the developmental process, akinetes showed a similar number of differentially expressed genes (497 genes), which were equally up- and down-regulated. The down-regulated genes were enriched in core metabolic functions, consistent with entry into a nongrowth state. There were relatively few adaptive genes up-regulated in 3-day akinetes, and there was little overlap with putative heterocyst developmental genes. There were 1,827 differentially transcribed genes in 24-h hormogonia, which was nearly fivefold greater than the number in akinete-forming or N(2)-fixing cultures. The majority of the up-regulated adaptive genes were genes encoding proteins for signal transduction and transcriptional regulation, which is characteristic of a motile filament that is poised to sense and respond to the environment. The greatest fraction of the 883 down-regulated genes was involved in core metabolism, also consistent with entry into a nongrowth state. The differentiation of heterocysts (steady state, N(2) grown), akinetes, and hormogonia appears to involve the up-regulation of genes distinct for each state.
authors.affiliation: Section of Microbiology, University of California, Davis, CA 95616, USA.
authors.forename: Elsie L
authors.initials: EL
authors.lastname: Campbell
authors.forename: Michael L
authors.initials: ML
authors.lastname: Summers
authors.forename: Harry
authors.initials: H
authors.lastname: Christman
authors.forename: Miriam E
authors.initials: ME
authors.lastname: Martin
authors.forename: John C
authors.initials: JC
authors.lastname: Meeks
mesh_terms: D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D002454:Cell Differentiation / Q000187:drug effects / Q000235:genetics; D020869:Gene Expression Profiling; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects; D005798:Genes, Bacterial; D016680:Genome, Bacterial; D009584:Nitrogen / Q000494:pharmacology*; D046937:Nostoc / Q000166:cytology / Q000187:drug effects / Q000235:genetics*; D020411:Oligonucleotide Array Sequence Analysis; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology
chemical_list: D001426:Bacterial Proteins; D000644:Quaternary Ammonium Compounds; D009584:Nitrogen