Comparison of Intraplasmid Rearrangements in Escherichia coli 

Luka Bočkor¹, Srećko Jelenić^†, Nenad Malenica, Jelena Mlinarec, Višnja Besendorfer and Ivana Ivančić-Baće^*

University of Zagreb, Faculty of Science, Department of Molecular Biology, Horvatovac 102a, HR-10000 Zagreb, Croatia
¹Current address: ICGEB, AREA Science Park, Padriciano 99, IT-34149 Trieste, Italy

Article history:
Received September 4, 2012
Accepted July 15, 2013

Key words:
RecA, intramolecular recombination, Agrobacterium tumefaciens, Escherichia coli

Summary:
In this work we have constructed a plasmid to compare intraplasmid recombination efficiency in Agrobacterium tumefaciens and Escherichia coli. The plasmid contains two directly repeated copies of spectinomycin resistance gene, one lacking 5’ and the other lacking 3’ end. These two copies share a 570-bp region of homology and are separated by the ampicillin resistance gene. Homologous recombination between repeated copies of incomplete spectinomycin resistance genes results in the restoration of spectinomycin resistance. During this process, ampicillin resistance gene is either deleted or incomplete spectinomycin genes are amplified along with the ampicillin resistance gene. This experimental system enabled us to follow for the first time the generation of deletions and amplifications during intraplasmid recombination in A. tumefaciens. We show here that predominantly RecA-independent mechanism contributes to the formation of deletion and amplification products in both, A. tumefaciens and E. coli. Additionally, deletion and amplification products were detected at similar frequencies, suggesting that amplifications and deletions probably occur by a similar mechanism.

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