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March 5, 2000


re: re: re: Does plant genome contains foreign DNA?


It would seem to me that the genetic engineering we
do on purpose is a lot safer than the breeding of the
past if for no other reason than we take a lot closer
look at the very small number of genes we are working
with insted of throwing every thing in a box, shaking it
up and hoping we get something better and not really
knowing what we have. It is certainly safer than irradiating
seed to induce mutation or inducing polyaploidy



Gordon Couger gcouger@couger.com

Stillwater, OK www.couger.com/gcouger
405 624-2855 GMT -6:00
From: "Casey"
> >Here is a question for AbBioView readers. Is there DNA evidence that the
> >plant genome contains foreign DNA? I can think of retrotransposons which
> >may by their movement activate endogenous genes and certainly this is
> >happening as an integral part of evolution. There is of course the DNA
> >ancient endosymbionts, some of which is now in the nucleus. Are there
> >other examples for the incorporation of DNA other than in pathogenicity
> >(eg Agrobacterium)?
> >
> >I probably should know the answer to this, but I cannot think of
> >
> >Maarten Chrispeels
> >
> >(University of California, San Diego)
> ---------------------
> Maarten
> I suspect you're trying to find evidence for 'natural' inter-species
> DNA/gene transfer. However, 'foreign' DNA is difficult to define. The
> simplest example, of course, is wheat - a Frankenstein 'natural' hybrid of
> three separate species. What is foreign DNA in this context? There is
> plenty of evidence for mammalian retroviruses transferring fragments of
> between genomes of host species - is this known in plants? For example,
> banana streak virus was unknown until breeders created Musa hybrids,
> resulting in activation of the integrated viral DNA, giving rise to
> infectious particles that now constitute a significant threat to banana
> production. Does the viral genome pick up and transfer bits of Musa DNA?
> This leads to an interesting point that I had intended bringing to
> AgBioView. In both mammals and plants we find that, in inter-species
> hybrids, dormant low-copy retrotransposons are activated and grossly
> amplified. The consequence of this massive number of random integration
> events is undoubtedly(?) massive and random disruption of genome function.
> Yet we observe the phenomenon, obviously, in viable hybrid progeny.
> One of the more sophisticated objections to GM plants is that, since we
> don't control the site of transgene integration, it could integrate into a
> site that subtly affects gene action, causing unpredictable and unknowable
> pleiotropic effects. Forgetting for a moment the empirical testing and
> analysis that is used to eliminate such events, the point I'm getting at
> that traditional plant breeding across species (within species?) causes
> genome disruption on a far, far greater scale than does integration of a
> single transgene. In other words, potential risks from unknown genomic
> disruption are far, far greater with traditional breeding than with
> transgenesis.
> Comments?