THE MECHANICS BY WHICH SCIENTISTS INTRODUCE NEW GENETIC MATERIAL INTO PLANTS ARE WELL KNOWN. THE POSSIBLE OUTCOMES ARE NOT AS WELL UNDERSTOOD.
May 4, 2000 / The Vancouver Sun
Carl Douglas, associate professor of plant molecular biology and head of the
department of botany at the University of British Columbia, writes that in
the debate over genetically modified plants, the question of how plant
biologists move genes around is not often addressed. But to assess possible
risks associated in the release of ``transgenic plants,'' it is important to
understand how gene transfers actually work.
Douglas says that generating transgenic plants is routine in research
laboratories, and can be done easily by students. However, it is not usually
done with the goal of producing genetically altered crops.
Rather, the goal is to introduce altered plant genes back into plants in
order to understand how plant genes control growth, development, metabolism
and the ability to withstand stresses such as pathogen attack, cold and
drought.
For decades, plant breeders have been moving groups of genes into crop
plants by crossing them with related wild species -- a process that is
difficult to control. Transfer of specific isolated genes to create
transgenic plants first became a reality in the late 1970s and early 1980s.
Douglas explains the basics of molecular biology and genetic engineering in
crops, and then says that in considering possible risks associated with such
transgenic crops, it is important to keep certain facts in mind. The T-DNA
is inserted into plant chromosomes randomly. This is a potential
disadvantage because it is possible that the inserted T-DNA will alter the
function of a normal plant gene.
However in most crop plants, genes are islands in a sea of non-functional
DNA, so that the T-DNA usually does not insert into a functional gene.
Furthermore, since T-DNA insertion is random, different transgenic plants
containing the same introduced gene will have that introduced gene at
different locations.
If insertion of a T-DNA fragment into one transgenic plant causes an
undesirable alteration, the chances that a second transgenic plant with the
same T-DNA will cause the same alteration is close to zero. Testing of
multiple, independent transgenic plants can easily exclude possible
undesired effects.
It is important to remember that gene rearrangements continually occur in
plants without human intervention. For example, maize and other crop plants
contain transposable elements -- naturally mobile genes that can freely
change position on plant chromosomes.
Plant genome projects also show that genetic material is naturally in a
state of flux. In the development of crop plants, humans have accelerated
this flux by selection and the large-scale mixing of distantly related
genetic material typical of plant breeding, and now through transfer of
specific genes.
There is always the possibility of undesirable alterations in crop plants by
natural and human-induced genetic changes. However, it is the overwhelming
view of the scientific community that any potential risks from transgenic
crop plants lie not in the process of gene transfer itself, but in the
functions of the transferred genes in the plant.
(posted without permission)
