Plant nodulation inducers enhance horizontal gene transfer of <i>Azorhizobium caulinodans</i> symbiosis island

Abstract

Significance Pathogenic or symbiosis islands are mobile genetic elements that can provide recipient bacteria the capacity to establish intimate interactions with eukaryotic hosts. For example, legume symbionts have evolved via horizontal transfer of symbiotic plasmids or genomic islands. Here, we show that the transfer of the symbiosis island of the Sesbania rostrata symbiont, Azorhizobium caulinodans , to other rhizobia is enhanced by plant flavonoids that also serve as signals to initiate the symbiotic process. These data suggest that eukaryotic hosts are involved in bacterial horizontal gene transfer to promote symbiotic interactions between rhizobia and legumes.