Feb 9, 2011 15:19 GMT  ·  By
Horizontal gene transfer may be rare, but it is also an under-researched mechanism
   Horizontal gene transfer may be rare, but it is also an under-researched mechanism

For many years, scientists have used the Tree of Life as a metaphor for the way life evolved over billions of years here on Earth. But new discoveries show that it may be more appropriate to call the whole thing the Mosaic of Life instead.

In the new investigation, it was revealed that a large gene cluster jumped species at at least one point in the history of life on our planet. This implies that evolution does not make life branch out gradually into increasingly more complex forms.

Rather than changes occurring in individual species over millions of years, it would seem that some changes are simply shifted from one organism to another directly. This is what happened to two fungus species at least once, experts behind the new work now say.

“The fungi are telling us something important about evolution […] something we didn't know,” explains Vanderbilt university assistant professor of biological sciences Antonis Rokas.

The expert and colleague Jason Slot, a research associate at the university, are also the authors of a new study detailing the findings, which are reported in the January 25 issue of the journal Current Biology.

The two experts have found conclusive evidence that a cluster of 23 genes “jumped” species several millions of years ago. The genetic material moved from the microorganism Aspergillus to Podospora.

The former is a mold strain that usually lives on foods that are rich in starch, including bread, potatoes and the likes. The latter is an organism that thrives in herbivore dung, where it plays an important role in breaking down plant fibers such as cellulose.

Throughout recent evolutionary history, there are only a few cases of this type of gene transfer taking place. Horizontal gene transfer is tremendously rare, and is even more so between the complex cells found in plants, animals and fungi.

“Because most people didn't believe that such large gene clusters could be transferred horizontally, they haven't looked for them and they haven't been found,” Rokas says, quoted by SpaceRef.

“Fungi produce an astonishing variety of drugs and poisons,” the expert goes on to add, saying that gene transfer is a method of boosting defenses against predators, while simultaneously strengthening attack mechanisms.

“Our discovery that one of the largest gene clusters responsible for making such a poison moved intact between species suggests that horizontal transfers of wholesale pathways may have contributed significantly to the generation of this diversity,” he concludes.