  The recA/RAD51 gene family encodes a diverse set of recombinase proteins that
effect homologous recombination, DNA-repair, and genome stability. The recA
gene family is expressed in almost all species of Eubacteria, Archaea, and
Eukaryotes, and even in some viruses. To date, efforts to resolve the deep
evolutionary origins of this ancient protein family have been hindered, in
part, by the high sequence divergence between families (i.e. ~30% identity
between paralogous groups). Through (i) large taxon sampling, (ii) the use of a
phylogenetic algorithm designed for measuring highly divergent paralogs, and
(iii) novel Evolutionary Spatial Dynamics simulation and analytical tools, we
obtained a robust, parsimonious and more refined phylogenetic history of the
recA/RAD51 superfamily. Taken together, our model for the evolution of
recA/RAD51 family provides a better understanding of ancient origin of recA
proteins and multiple events leading to the diversification of recA homologs in
eukaryotes, including the discovery of additional RAD51 sub-families.
