Phylogenetic analysis reveals gene conversions in multigene families of rhizobia

Gene families are an important and intrinsic trait of rhizobial species. These gene copies can participate in non-reciprocal recombination events, also called gene conversions. Gene conversion has diverse roles, but it is usually implicated in the evolution of multigene families. Here, we searched for gene conversions in multigene families of six representative rhizobial genomes. We identified 11 gene families with different numbers of copies, genome location and function in CFN42 and CIAT652 strains of Rhizobium etli, Rhizobium sp NGR234, Mesorhizobium loti MAFF303099, Sinorhizobium meliloti 1021, and Bradyrhizobium japonicum USDA110. Gene conversions were detected by phylogenetic inference in the nifD and nifK gene families in R. etli. Sequence analysis confirmed multiple gene conversions in these two gene families. We suggest that gene conversion events have an important role in homogenizing multigene families in rhizobia.