Biotech boosters are claiming support for the "naturalness" of genetic modification from the occurrence of "cross kingdom" gene movement in nature (see items 2 and 3). While there is evidence for such occurrences, in what appear at the moment to be limited circumstances, but as E. Ann Clark points out (in an earlier post - item 1 below) the scale and time- frame for such changes is vastly different to what is occurring with GM crops.
1. "What is Natural?" - Dr E.Ann Clark
2. Tumor-Causing Plant Bacteria May Infect Human Cells (Reuters)
3. Earlier evidence of trans-kingdom movement of DNA - 2 Nature refs
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1. "What is Natural?"
E. Ann Clark
University of Guelph
SANET Post
February 3, 1999
http://www.biotech-info.net/natural2.html
Folks: One of the most common responses I hear from my colleagues about the "unnaturalness" of GE organisms is that genes have been moving among species, genera, and even wider ranges of genetic backgrounds throughout evolution. Evidence exists of viruses, for example, inserting themselves into many different genomes, some on a relatively permanent basis, and presumably influencing the direction of natural selection and evolution. I am out of my depth on this, and would appreciate correction if I am off base, but I think it is fair to accept the fact that genes have been moving among unrelated organisms for a long time.
If so, then how is GE different from nature? I have been thinking for some time about the issue of scale - in both space and time. In nature, let's imagine that an individual virus manages to insert itself, de novo, into another organism - say an individual squash plant, and in so doing, affects the fitness and survival of that individual plant. Sometimes good, sometimes bad, - the whole natural selection thing over hundreds, thousands....etc. years. But the key issue is that it is a *point* process occurring in a single individual, and the outcome of that single event is acted upon by selection over a very long time.
But most importantly, the outcomes are not limited to that individual squash plant, but to all the other organisms and ecological processes affected by that pivotal squash plant. The affected would include the pests, predators, herbivores, and other neighboring plants of that individual plant and its progeny, as well as the decomposer organisms that break down the residues and so on. What matters, in an ecosystem sense, is not just the fitness of the squash caused by the individual genetic event of inserting viral genes, but everything else that follows. Nature has time to adjust, for co-evolution in affected organisms to occur, and for the ultimate fitness of the trait to be tested.
Understand that I am willing to assume zillions of examples of this kind of thing are happening all the time, but in each case, it is a point source of genetic variation, analogous to a mutation, and the ultimate outcome (favorable, unfavorable) takes many many years to manifest itself. The degree to which "foreign" genes exist today, in our own genome and that of other ife forms is a reflection of the winners - the ones that managed to hang together for whatever reason.
Now, how is this different from GE? Compare the tortuously slow and convoluted process of natural selection acting on a point source of genetic variation, throughout an ecosystem, with the instantaneous entry of a single, novel genome over millions of hectares of agricultural land. Instead of a single individual plant, responding to multifaceted selection pressure exerted by the weather, neighbors, pest, herbivores, etc., we have zillions of identical plants all doing the same thing, growing the same plant pesticide, pumping the same, novel active Bt toxin in the soil all at the same time (novel because it is in the active form, not a precurser).
There is no time for nature to sort things out, to screen out the deleterious and encourage the favorable. I wonder if this might not be a key difference between gene movement in "nature" and via GE.
Ann
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2. Tumor-Causing Plant Bacteria May Infect Human Cells
Emma Patten-Hitt REUTERS Health News Wednesday, 31 January 2001.
NEW YORK - A soil bacterium that causes lumpy tumors on plants may be able to 'jump kingdoms' and insert its tumor-causing DNA into human cells, new research findings suggest. The bacterium, called Agrobacterium tumefaciens, contains a small piece of DNA that can insert itself into the DNA of a host cell and initiate a tumor. Agrobacterium is already known to cause plant tumors, but researchers wanted to test whether the bacterium could similarly insert its DNA into human cells.
Dr. Vitaly Citovsky from the State University of New York, Stony Brook, and colleagues found that the plant bacterium was able to attach to human cells and insert its DNA into human cells just as it does with plant cells. Whether Agrobacterium is dangerous to humans is unclear, however. "Here (insertion of DNA into) human cells has been observed in laboratory conditions; whether it may be relevant biologically in nature remains unknown,'' the researchers note in the current early edition of the Proceedings of the National Academy of Sciences.
"Our experiments were done under laboratory conditions,'' Citovsky told Reuters Health. "In nature, I do not believe Agrobacterium represents a danger. However, for people who work with large concentrations of this bacterium, for example researchers or certain agricultural workers who deal with heavily infected plants, it may be prudent to be careful or at least aware,'' he said.
One implication of this study, said Citovsky, is the potential for genetic flow between bacteria and animals. Another implication is that the basic biochemical and cellular reactions involved in the Agrobacterium-plant cell interaction probably exist in the animal kingdom as well.
"Presently, it appears that Agrobacterium is the only example of trans-kingdom DNA transfer,'' Citovsky said. "I do not rule out other possibilities but there are no data. Of course, what can be done once, can almost always be done again,'' he added. SOURCE: Proceedings of the National Academy of Sciences Early Edition -End of Reuter Item
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3. Earlier evidence of trans-kingdom movement of DNA
Bacterial conjugative plasmids bacteria and yeast, Nature, 1989 Jul 20;340(6230):205
Movement of shuttle plasmids from Escherichia coli into yeasts other than Saccharomyces cerevisiae using trans-kingdom conjugation, Plasmid 1993 Nov;30(3):251-7