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Anabaena xisF gene encodes a developmentally regulated site-specific recombinase
C D Carrasco1, K S Ramaswamy, T S Ramasubramanian
1Department of Biology, Texas A&M University, College Station 77843-3258.
Genes & Development
|January 1, 1994
Summary
The gene xisF drives DNA excision during Anabaena heterocyst differentiation. Its inactivation prevents element removal and nitrogen-fixing growth, but heterocyst development proceeds, indicating additional regulatory factors.
Area of Science:
- Microbiology
- Molecular Biology
- Genetics
Background:
- Anabaena undergoes heterocyst differentiation, a process involving programmed DNA excision.
- Two DNA elements are removed from the chromosome during this developmental transition.
Purpose of the Study:
- To identify the gene encoding the recombinase responsible for excising a specific DNA element within the fdxN gene.
- To investigate the function of this recombinase in Anabaena heterocyst differentiation and DNA rearrangement.
Main Methods:
- Cloning and expression of the xisF gene in Escherichia coli to test its recombinase activity.
- Gene inactivation of xisF in the Anabaena chromosome.
- Analysis of DNA excision, heterocyst development, and growth under nitrogen-deficient conditions.
Main Results:
- The gene xisF encodes the site-specific recombinase for the 55-kb element excision from the fdxN gene.
- Cloned xisF induced site-specific rearrangement in E. coli.
- xisF inactivation blocked element excision and nitrogen-fixing growth but not heterocyst formation.
- Forced xisF transcription in vegetative cells did not trigger excision.
Conclusions:
- XisF is essential for the excision of the fdxN element, crucial for nitrogen-fixing growth.
- Heterocyst development is separable from this specific DNA excision event.
- Additional factors likely regulate xisF activity for cell-type specificity during differentiation.