Throughout the evolution of life on earth, bits of genetic material are routinely swapped among different species of bacteria to give them a competitive advantage. But rarely do such gene transfers happen between bacteria and higher organisms.
Now, Prof. Nikolas Nikolaidis, et. al., report on a rare case where plant genes called expansins, which are responsible for loosening or weakening protective cell wall, were transferred from plants to bacteria, fungi and amoeba that are known plant pathogens or live nearby in the soil.
"Our study reveals a rare phenomenon in molecular evolution where plant genes have been transferred to simpler organisms like fungi and bacteria," said Nikolaidis. "The protein products of these genes are weakening the plant cell wall allowing plants to grow. In the case of bacteria and fungi, these proteins are related with the ability of these species to colonize plant roots and their virulence as plant pathogens. Our study suggests that by using proteins acquired from their hosts bacteria and fungi have found new adaptive ways to utilize their hosts resources and maybe become more advanced pathogens."
The research team found two independent instances of such horizontal gene transfers that occurred from plants to bacteria and fungi. These events were followed by gene swapping amongst bacteria and fungi to refine their evolutionary fitness. The authors also looked at the details of the gene swapping at the molecular level, and found fused DNA segments that point to a similar gene function, binding to plant and bacteria cell walls.
The evolution of these non-plant expansins represents a unique case in which bacteria and fungi have found innovative and adaptive ways to interact with and infect plants. This evolutionary paradigm suggests that, despite their low frequency, such rare events have contributed significantly in the evolution of prokaryotic and eukaryotic species.
|Contact: Joe Caspermeyer|
Molecular Biology and Evolution (Oxford University Press)