Evolutionary persistence of tripartite integrative and conjugative elements

In this study, examination of ICE3s revealed that most symbiosis genes are carried on the large α fragment. Some ICE3-β and γ regions also carry genes that potentially contribute to the symbiosis, or to persistence in the soil environment, but these regions have been frequently subjected to recombination events including deletions, insertions and recombination with genes located on other integrative elements. Examination of a new ICE3 in M. ciceri Ca181 revealed it has jettisoned the genetic cargo from its β region and recruited a serine recombinase gene within its γ region, resulting in replacement of one of the three ICE3 integration sites. Overall the recombination loci appear to be the only conserved features of the β and γ regions, suggesting that the tripartite structure itself provides a selective benefit to the element. We propose the ICE3 structure provides enhanced host range, host stability and resistance to destabilization by tandem insertion of competing integrative elements. Furthermore, we suspect the ICE3 tripartite structure increases the likelihood of gene capture from integrative elements sharing the same attachment sites.

Source: Plasmid - June 30, 2017 Category: Biotechnology Source Type: research