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Date:

March 5, 2000

Subject:

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

Gordon Couger gcouger@couger.com

Stillwater, OK www.couger.com/gcouger
405 624-2855 GMT -6:00
From: "Casey"
To:
> >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
of
> >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
examples.
> >
> >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
DNA
> 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
is
> 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?