Heterocysts are microaerobic, N-fixing cells that form in a patterned array within O-producing filamentous cyanobacteria. Structural features of heterocysts can be predicted from consideration of their physiology. This review focuses on the spacing mechanism that determines which cells will differentiate, and on the regulation of the progression of the differentiation process. Applicable genetic tools, developed primarily using PCC 7120, but employed also with spp., are reviewed. These tools include localization of transcription using fusions to , and , and mutagenesis with -containing derivatives of transposon Tn. Mature and developing heterocysts inhibit nearby vegetative cells from differentiating; genes , and the locus may hold keys to understanding intercellular interactions that influence heterocyst formation. Regulatory and other genes that are transcriptionally activated at different times after nitrogen stepdown have been identified, and should permit analysis of mechanisms that underlie the progression of heterocyst differentiation.

Keyword(s): akinetesAnabaenaNostocpatternspacing

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  • Article Type: Review Article
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