skip to main content


Title: The repABC plasmids with quorum-regulated transfer systems in members of the Rhizobiales divide into two structurally and separately evolving groups

The large repABC plasmids of the order Rhizobiales with Class I quorum-regulated conjugative transfer systems often define the nature of the bacterium that harbors them. These otherwise diverse plasmids contain a core of highly conserved genes for replication and conjugation raising the question of their evolutionary relationships. In an analysis of 18 such plasmids these elements fall into two organizational classes, Group I and Group II, based on the sites at which cargo DNA is located. Cladograms constructed from proteins of the transfer and quorum-sensing components indicated that those of the Group I plasmids, while coevolving, have diverged from those coevolving proteins of the Group II plasmids. Moreover, within these groups the phylogenies of the proteins usually occupy similar, if not identical, tree topologies. Remarkably, such relationships were not seen among proteins of the replication system; although RepA and RepB coevolve, RepC does not. Nor do the replication proteins coevolve with the proteins of the transfer and quorum-sensing systems. Functional analysis was mostly consistent with phylogenies. TraR activated promoters from plasmids within its group, but not between groups and dimerized with TraR proteins from within but not between groups. However, oriT sequences, which are highly conserved, were processed by themore » transfer system of plasmids regardless of group. Here, we conclude that these plasmids diverged into two classes based on the locations at which cargo DNA is inserted, that the quorum-sensing and transfer functions are coevolving within but not between the two groups, and that this divergent evolution extends to function.« less
 [1] ;  [2] ;  [1] ;  [1]
  1. Univ. of Illinois at Urbana-Champaign, Urbana, IL (United States). Dept. of Microbiology
  2. Univ. of Illinois at Urbana-Champaign, Urbana, IL (United States). Dept. of Microbiology and Carl R. Woese Inst. for Genomic Biology
Publication Date:
Grant/Contract Number:
SC0006642; AC02-06CH11357
Accepted Manuscript
Journal Name:
Genome biology and evolution
Additional Journal Information:
Journal Volume: 7; Journal Issue: 12; Journal ID: ISSN 1759-6653
Society for Molecular Biology and Evolution
Research Org:
Univ. of Illinois at Urbana-Champaign, Urbana, IL (United States)
Sponsoring Org:
USDOE Office of Science (SC), Biological and Environmental Research (BER) (SC-23)
Country of Publication:
United States
59 BASIC BIOLOGICAL SCIENCES; plasmid evolution; RepABC; horizontal transfer; quorum-sensing; Alphaproteobacteria; conjugative transfer genes; multiple sequence alignment; complete nucleotide-sequence; tumefaciens ti plasmid; etli symbiotic plasmid; tumor-inducing ti; trar-like protein; broad-host-range; sp strain ngr234; agrobacterium-tumefaciens; conjugal transfer
OSTI Identifier: