Cyanobacterial cell lineage analysis of the spatiotemporal hetR expression profile during heterocyst pattern formation in Anabaena sp. PCC 7120

• Published in: PloS one 2009-10, Vol.4 (10), p.e7371-e7371
• Main Authors: Asai, Hironori, Iwamori, Shunsuke, Kawai, Kentaro, Ehira, Shigeki, Ishihara, Jun-ichi, Aihara, Kazuyuki, Shoji, Shuichi, Iwasaki, Hideo
• Format: Article
• Language: English
• Subjects: Anabaena; Anabaena - genetics; Anabaena cylindrica; Analysis; Bacteria; Bacterial Proteins - metabolism; Cell Biology/Morphogenesis and Cell Biology; Cell culture; Cell cycle; Cell differentiation; Cell Division; Cell lineage; Cyanobacteria; Cyanobacteria - cytology; Cyanobacteria - metabolism; Cytological Techniques; Deoxyribonucleic acid; Developmental Biology/Cell Differentiation; Developmental Biology/Pattern Formation; Differentiation (biology); DNA; Dynamic tests; Electrical engineering; Filaments; Fluorescence; Fluorescent Dyes - chemistry; Gene expression; Gene Expression Regulation, Bacterial; Green Fluorescent Proteins - metabolism; Heterocysts; Liquid culture; Microbiology/Microbial Growth and Development; Microscopy, Electron, Scanning - methods; Microscopy, Fluorescence - methods; Models, Biological; Morphogenesis; Morphology; Nitrogen; Nitrogen - chemistry; Nitrogen - metabolism; Nitrogen Fixation; Pattern formation; Patterning; Proteins; Science; Statistical analysis; Stochastic models; Stochastic processes; Stochasticity
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0007371

Diazotrophic heterocyst formation in the filamentous cyanobacterium, Anabaena sp. PCC 7120, is one of the simplest pattern formations known to occur in cell differentiation. Most previous studies on heterocyst patterning were based on statistical analysis using cells collected or observed at different times from a liquid culture, which would mask stochastic fluctuations affecting the process of pattern formation dynamics in a single bacterial filament. In order to analyze the spatiotemporal dynamics of heterocyst formation at the single filament level, here we developed a culture system to monitor simultaneously bacterial development, gene expression, and phycobilisome fluorescence. We also developed micro-liquid chamber arrays to analyze multiple Anabaena filaments at the same time. Cell lineage analyses demonstrated that the initial distributions of hetR::gfp and phycobilisome fluorescence signals at nitrogen step-down were not correlated with the resulting distribution of developed heterocysts. Time-lapse observations also revealed a dynamic hetR expression profile at the single-filament level, including transient upregulation accompanying cell division, which did not always lead to heterocyst development. In addition, some cells differentiated into heterocysts without cell division after nitrogen step-down, suggesting that cell division in the mother cells is not an essential requirement for heterocyst differentiation.