The paper is freely available in PNAS (Proceedings of the National Academy of Sciences. My mom freaked out the first time she heard me jokingly call the journal "pee-nass" after they rejected one of my papers during grad school). The paper starts by defining horizontal gene transfer. This naturally occurring process is when a gene goes from one species to another, and has been studied quite a bit in bacteria. Scientists are starting to identify instances of horizontal gene transfer in non-bacterial organisms: sometimes the gene that gets transferred ends up being non-functional, but sometimes it does. So horizontal gene transfer can also be important in the evolution of species.
When anti-GMO activists claim that GMOs are not natural because scientists are taking a gene from one species and adding it to another, it is often pointed out that horizontal gene transfer happens "naturally" without any human intervention. To understand this point (and the importance of this paper), it is necessary to explain one of the more common methods that scientists use for transgenesis: Agrobacterium-mediated transformation.
|Agrobacterium induced gall (Wikimedia commons)|
Agrobacterium-Mediated TransformationThe summary below is from this freely available review (any additional references are indicated). The Agrobacterium genus has many different bacteria that cause different plant diseases. For genetic engineering, the species used is Agrobacterium tumefaciens which causes crown gall disease. Crown galls are growths on plants, similar to tumors. When the spouse read this, he pointed out that many of the gardening books that he's read highlight the fact that you're not supposed to use pruning shears on plants that have galls without cleaning them, so that you don't transfer the bacteria from one plant to another. Galls develop when a chunk of DNA from the bacteria, known as Ti-DNA (Tumor inducing) gets added to the plant's own DNA. For this to happen, the DNA needs to get cut out of the bacteria, transported into the plant cell, and integrated into the plant's genome. This process is carried out by proteins that are made by the bacteria known as vir genes (virulence), and there's quite a few of them that perform different tasks in the transformation process.
|Crown gall caused by Agrobacterium (Wikimedia commons)|