Genes are normally transferred ‘vertically’ from parent to offspring. For the past few decades, biologists have become increasingly aware of the importance of ‘horizontal’ transfer in which individuals, almost exclusively microorganisms, acquire genes from their neighbors. Jason Slot and Antonis Rokas of Vanderbilt University document a case of horizontal transfer in fungi.
A 23 gene cluster responsible for the entire production pathway of sterigmatocystin, a toxin, was transferred from the fungus Aspergillus nidulans to the fungus Podospora anserine. In case you’re wondering how different two fungi could possibly be, these particular fungi occupy two different taxonomic classes. To put that in perspective, all mammals constitute a single class.
As of now, although plentiful in bacteria, only a few cases of horizontal transfer are known in multicellular organisms and the exact mechanism in these complex organisms is not yet known. However, the researchers speculate that this type of genetic shuffling may have played a larger roll in generating genetic diversity than previously thought. If that's true, biologists may have to rethink the traditional 'tree of life'.
You can see an explanation by Slot and Rokas below:
Top: photo of Aspergillus nidulans by Plasmidmap, 12/3/2007.