GE - US analysis - GE is not extension of conventional plant breeding

["NLP Wessex" <nlpwessex@bigfoot.com>(by way of GEN lists <genetics@gn.apc.org>)]

The following analysis of the profound difference between genetic
engineering (also known as 'genetic modification') and conventional breeding
in plant science is by Dr Michael Hansen of the US Consumers Union. Dr
Hansen was one of the key people responsible for exposing the damaging
effects of genetically modified BST used (still to this day) in US milk
production, and now banned in both the European Union and Canada.

As this highly useful analysis goes into some considerable detail we provide
immediately below some particular extracts (full version at bottom of
message covering:  gene tranfer scope, gene location insertion and
vector/promoter usage).  The full text is also available online at
<http://www.biotech-info.net/wide_crosses.html>http://www.biotech-info.net/
wide_crosses.html (Ag Biotech InfoNet site -
highly recommended) for those who wish to provide links to their own sites.

Remember how safe and sustainable the scientists said nuclear power was
going to be? Given a choice between living near a conventional power station
or a nuclear power station (using Hansen's interesting analogy) most of us
would likely chose the conventional one.

GE is to the food supply what nuclear power is to the energy supply - an
option that turned out to be not such a good idea after all decades later -
as large numbers of people in the Ukraine and surrounding countries have
found to their cost.

Hansen's 'pea' analogy in relation to the FDA's evasive GE food labelling
policy is therefore also highly telling.

NATURAL LAW PARTY WESSEX
nlpwessex@bigfoot.com
<http://www.btinternet.com/~nlpwessex>www.btinternet.com/~nlpwessex
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Extracts from: 'Genetic Engineering is not an extension of conventional
plant breeding' Michael K. Hansen Ph.D, Consumer Policy Institute/Consumers
Union, USA, January 2000
............................................................................
...........

"Genetic engineering is not just an extension of conventional breeding. In
fact, it differs profoundly....

As for the scope of genetic material transferred, genetic engineering allows
the movement of genetic material from any organism to any other organism. It
also offers the ability to create genetic material, and expression products
of that material, that have never existed before....

Virtually all crop plants derived via GE also contain a powerful promoter (a
genetic regulatory or "on"-switch) from the Cauliflower mosaic virus (the
CaMV 35S promoter), which in nature causes a disease in plants in the
mustard family.....The CaMV 35S promoter is used precisely because it is
such a powerful promoter, which leads to hyperexpression of the transgenes,
having them be expressed at perhaps 2 to 3 orders of magnitude higher than
of the organism's own genes. The CaMV 35S promoter effectively puts the
transgene(s) outside of virtually any regulatory control by the host genome
as the natural plant promoters for each gene allow....

Use of such strong promoters also raise safety concerns. Since the CaMV 35S
is so strong, not only can it affect the introduced transgenes, it can also
affect genes (either turn them "on" or turn them "off") thousands of base
pairs upstream and downstream from the insertion site on a given chromosome
and even affect behavior of genes on other chromosomes. Consequently,
depending on the insertion site, a gene that codes for a toxin could be
turned "on," leading to production of that toxin....

We see genetic engineering as a quantum leap from conventional breeding-as
different from it as nuclear power generation is from a coal-fired plant....

Labeling would not be a deviation from previous FDA policy. Indeed, the
failure to require labeling is a deviation from previous FDA policy. The
difference between frozen peas and fresh peas, one could easily argue, is
much less than the difference between genetically engineered peas and
conventional peas. The frozen and fresh peas can be genetically identical.
The frozen peas may even be nutritionally superior, even as consumers choose
fresh peas thinking fresh is better. Yet FDA appropriately requires labeling
about the difference, and allow consumers to make their own choices about
what to buy....

Additional reasons to label include helping consumers manage food allergies
and sensitivities and allowing the public health community to track and
identify any unexpected effects.......

The science is also clear that this unique and identifiable process of
genetic engineering creates a new and unique potential for unexpected
effects, due to the unique nature of the material being inserted, from a
genome which has not previously interacted with the host genome, due to lack
of control over the location at which the gene is inserted, and due to the
introduction the CaMV "promoter" gene, which overrides the existing genetic
programming. FDA therefore has an obligation to require mandatory reviews of
all genetically engineered food before it goes on the market, and develop
ways to screen for unexpected effects which could have health consequences.

There are also predictable risks, such as potential risks of toxins,
allergens and nutritional changes and antibiotic marker genes, which FDA
should address...... "

............................................................................
....
For more material by Hansen on GE issues see:
'Why we need labelling of genetically engineered food' - see
<http://www.consunion.org/food/whywenny798.htm>http://www.consunion.org/foo
d/whywenny798.htm

'Potential Public Health Impacts Of The Use Of Recombinant Bovine
Somatotropin In Dairy Production'
<http://www.igc.org/consunion/food/bgh-abstract.htm>http://www.igc.org/cons
union/food/bgh-abstract.htm
............................................................................
....
For more material on risks associated with the CaMV 35S promoter and other
aspects of GE - see
<http://www.btinternet.com/~nlpwessex/Documents/camv.htm>www.btinternet.com/
~nlpwessex/Documents/camv.htm
<http://www.btinternet.com/~nlpwessex/Documents/gmrisk.htm>http://www.btint
ernet.com/~nlpwessex/Documents/gmrisk.htm
<http://ww.btinternet.com/~nlpwessex/Documents/compliance.htm>http://ww.bti
nternet.com/~nlpwessex/Documents/compliance.htm

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"GENETIC ENGINEERING IS NOT AN EXTENSION OF CONVENTIONAL PLANT BREEDING: How
genetic engineering differs from conventional breeding, hybridization, wide
crosses and horizontal gene transfer"

Michael K. Hansen, Ph.D.
Research Associate
Consumer Policy Institute/Consumers Union
January, 2000

Genetic engineering is not just an extension of conventional breeding. In
fact, it differs profoundly. As a general rule, conventional breeding
develops new plant varieties by the process of selection, and seeks to
achieve expression of genetic material which is already present within a
species. (There are exceptions, which include species hybridization, wide
crosses and horizontal gene transfer, but they are limited, and do not
change the overall conclusion, as discussed later.) Conventional breeding
employs processes that occur in nature, such as sexual and asexual
reproduction. The product of conventional breeding emphasizes certain
characteristics. However these characteristics are not new for the species.
The characteristics have been present for millenia within the genetic
potential of the species.

Genetic engineering works primarily through insertion of genetic material,
although gene insertion must also be followed up by selection. This
insertion process does not occur in nature. A gene "gun", a bacterial
"truck" or a chemical or electrical treatment inserts the genetic material
into the host plant cell and then, with the help of genetic elements in the
construct, this genetic material inserts itself into the chromosomes of the
host plant. Engineers must also insert a "promoter" gene from a virus as
part of the package, to make the inserted gene express itself. This process
alone, involving a gene gun or a comparable technique, and a promoter, is
profoundly different from conventional breeding, even if the primary goal is
only to insert genetic material from the same species.

But beyond that, the technique permits genetic material to be inserted from
unprecedented sources. It is now possible to insert genetic material from
species, families and even kingdoms which could not previously be sources of
genetic material for a particular species, and even to insert
custom-designed genes that do not exist in nature. As a result we can create
what can be regarded as synthetic life forms, something which could not be
done by conventional breeding.

It is interesting to compare this advance to the advances that led to
creation of synthetic organic chemicals earlier in the 1900s. One could
argue that synthetic chemicals are just an extension of basic chemistry, and
in certain senses they are. Yet when we began creating new chemicals that
had not previously existed on the earth, or which had only been present in
small quantities, and began distributing them massively, we discovered that
many of these chemicals, even though they were made of the same elements as
"natural" chemicals, had unexpected adverse properties for the environment
and health. Because we had not co-evolved with them for millenia, many
(though by no means all) had negative effects. Among the serious problems
were PCBs and vinyl chloride, which were found to be carcinogens, and
numerous organochlorine pesticides, which were found to be carcinogens,
reproductive toxins, endocrine disruptors, immune suppressors, etc. After
several decades of use, these effects caused such concern that we passed the
Toxic Substances Control Act which required premarket screening of synthetic
organic chemicals by EPA for such effects as carcinogenicity, mutagenicity
and impact on wildlife, and changed our pesticide rules similarly. There are
many ways in which these two scientific advances are not analogous, but the
experience with synthetic organic chemicals underlines the potential for
unexpected results when novel substances are introduced into the biosphere.

We will discuss three specific ways in which genetic engineering differs
from conventional breeding, and some of the implications for safety, in more
detail. The argument is frequently made that genetic engineering is not only
an extension of conventional breeding, but is more precise, and therefore
safer. We believe that in fact it represents a quantum leap from
conventional breeding, is more precise in one way, but more unpredictable in
others. We will discuss the following key areas of difference and their
implications for unexpected effects: scope of genetic material
transferred/unnatural recombination, location of the genetic insertions, and
use of vectors designed to move and express genes across species barriers.
As a subset of the last category there is the use of foreign promoters
(genetic "on" switches) and foreign marker genes (particularly genes coding
for antibiotic resistance). Finally we will discuss implications for FDA
policy.

Scope of Gene Transfers
.....................................

As for the scope of genetic material transferred, genetic engineering allows
the movement of genetic material from any organism to any other organism. It
also offers the ability to create genetic material, and expression products
of that material, that have never existed before.

This radically differs from traditional breeding, which merely permits the
movement of genetic material between different varieties within species,
between closely related species, or closely related genera. Even
hybridization and wide crosses cannot move genetic material much beyond
these limits. The vast bulk of hybrid crops consist of the mating of two
genetically pure lines (i.e. lines that are homozygous for all alleles) of
the same crop to create a line which is heterozygous. Thus, hybrid corn is
simply the crossing of two pure corn varieties to produce a mixed line.
Occasionally, though, in conventional breeding, plant breeders will cross a
wild relative of a crop (usually a different species within the same genus)
in order to transfer particular traits from that wild relative (such as
resistance to a given disease) to the crop. However, hybrids between two
species are also known to occur naturally, although such hybrids are
primarily restricted to plants with certain characteristics-such as
perennial growth habit-which most crop plants lack (Ellstrand et al., 1996).

Wide crosses, also used by breeders, also occur in nature, but they are
rare. When breeders perform wide crosses, they mate two different genera.
While the pollen of species A may successfully fertilize the egg of species
B, the embryo may not be able to naturally survive and develop into a
seedling. The plant breeder, through a technique called embryo rescue, will
remove such an embryo from the original hybrid seed and put it into a
nutritional environment in the laboratory (one containing various nutrients
and plant hormones) and raise it into seedling and adult plant. While such
wide crosses are artificial in one sense (the plant wouldn't normally
germinate or survive to adulthood), they still represent the mixing of
genomes from plants that are fairly closely related and in which
fertilization can occur. Wide crosses will happen between plants from two
different genera within the same family and often the same sub-family. Wide
crosses cannot be achieved with plants from widely different families. Thus,
while wide crosses, as breeders perform them, do not occur in nature, they
represent only a slight stretching of the boundaries of what can occur in
nature. In a sense wide crosses represent a stretching of these boundaries
by inches compared to miles with GE. After all, with GE, one can mix genes
not only from widely different plant families, one can put genes from any
organism on earth, or can create genes which have not existed before and put
them, into plants.

The mixing of genes from very different sources is likely to introduce new
elements of unpredictability. Because conventional breeding, including
hybridization and wide crosses, permits the movement of only an extremely
tiny fraction of all the genetic material that is available in nature, and
only allows mixing, and recombination, of genetic material between species
that share a recent evolutionary history of interacting together, one would
expect that the products of conventional breeding would be more stable and
predictable. The genome is a complex whole made up in part of genes and
genetic elements that interact in complex regulatory pathways to create and
maintain the organism. Any new genetic material that enters the genome must
fit into this complex regulatory whole or it may end up destabilizing the
whole. Think of the genome as a complex computer program or as an ecological
community. When one introduces a new subprogram within the larger complex
computer program, no computer programmer can reliably predict what will
happen. Because of the complexity of such large programs, a small new
subprogram can have unpredictable effects and may ultimately cause the whole
program to crash. With a complex ecosystem, the introduction of a new
species can have a range of effects, from virtually nothing to a
catastrophic effect on the ecosystem; most of these changes cannot be
reliably predicted knowing just the biology of the introduced species.

The view that genetic engineering may be more prone to unexpected outcomes
because it creates profound disruption in the normal interactions of genes
is supported by differences in the success rate in producing viable stable
offspring, for genetic engineering versus conventional breeding. In nature,
most offspring are viable; the vast majority of seeds germinate and produce
organisms that survive and reproduce. In conventional breeding, scientists
grow many plants and keep only a few with the most desirable traits; however
the ones they discard are still almost always normal examples of the
species. This is not true for products of genetic engineering. In the early
days of GE, although one could select cells which contained and expressed
the desired trait (due to the use of marker genes), it was necessary to
attempt to grow the engineered cells into whole plants to determine the
overall impacts of the GE. A very large percentage of the transformed cells
either were not viable, were grossly deformed, or failed to stably
incorporate the desired trait, i.e. failed to produce that trait in the
plant in successive generations (Crouch, personal communication). Some of
the malformations may be due to difficulties with tissue culture of the
transformed cells; however unexpected genetic effects also appear to be a
causative factor. In fact, only one in thousands (or tens of thousands or in
some cases even millions) of attempts achieves the desired results in terms
of a seed that incorporates the desired traits, and expresses them in a
useful fashion generation after generation, and doesn't have undesirable
side effects. Assertions that genetic engineering is a highly precise
process therefore seem misleading.

Location of Gene Insertion
........................................

GE can control relatively precisely the trait that is being inserted into a
host plant genome. However it cannot yet control the location where the
trait is inserted into the genome with any precision, nor guarantee stable
expression of the transgene. The process of insertion of foreign genetic
material via GE into the host plant genome and the expression of such
material is called transformation. Transformation is currently accomplished
through several relatively crude methods which are relatively random in
where the genes end up. One transformation method frequently used consists
of a manipulating a bacteria in the genus Agrobacterium. These bacteria are
among the few known which can transfer their genetic material to another
kingdom/phyla. These bacteria cause a disease in plants (either a tumor-like
growth called crown gall disease at the infection site, or uncontrolled
sprouting of roots from the infection site) by attaching to the plants,
transferring bacterial DNA into the plant and getting that DNA incorporated
into the host plant genome. Agrobacterium-mediated plant transformation
involves engineering the Agrobacterium by deleting the disease-inducing
genes, retaining the bacterial transfer DNA (T-DNA) and inserting the
genetic traits/elements to be transferred. This engineered Agrobacterium,
sometimes called a bacterial "truck" is then just mixed with the desired
plant cells and allowed to transform/infect them. The use of
Agrobacterium-mediated transformation occurs primarily with dicots
(non-grass like plants) and is difficult to do with grains.

The direct gene introduction methods include chemical treatment or
electroporation of protoplasts and use of the "gene gun." Chemical treatment
or electroporation consists of exposing plants to chemicals or an electrical
field that makes the protoplasts' cell membrane more "porous" facilitating
the uptake of DNA from the surrounding medium. The gene gun is used to
"shoot" microscopic particles (such as gold) covered with DNA into the plant
tissues themselves. In all three cases, once the DNA is in the plant cell it
still needs to be incorporated in the host genome. This is done using
genetic elements (T-DNA) from Agrobacterium. The direct gene introduction
methods are often used in transforming cereals which are fairly resistant to
Agrobacterium-mediated transformation. Furthermore, the direct introduction
methods routinely lead to insertion of multiple copies of the genetic
construct either at a single site or in multiple locations in the host
genome. Agrobacterium-mediated transformation, on the other hand, usually
leads to insertions at a single site in the plant genome. In either case,
however, the site or sites are fairly random. Because the effect of a gene
on the whole organisms is significantly governed by its location, the lack
of control over location is a significant cause of unexpected effects.

In terms of the location of genetic material in traditional breeding, since
it occurs between organisms that share a recent evolutionary background, it
involves the shuffling around of different versions (called alleles) of the
same gene. Furthermore, these genes are usually fixed in their location on
the chromosome by evolution. With GE, the genetic insertion happens in
unpredictable places which can lead to unpredictable effects. Thus in this
key regard, genetic engineering is more random than conventional breeding.

A clear example of unpredictability was seen in an experiment performed with
Arabidopsis thaliana, a plant in the mustard family that is frequently used
for biological research (Bergelson et al., 1998). The experiment compared
several lines, one developed by conventional breeding, and two by genetic
engineering, that all exhibited the same trait of herbicide tolerance.
Researchers at the University of Chicago induced herbicide (chlorsulphuron)
tolerance (HT) into A. thaliana via a form of conventional breeding called
mutation breeding and via GE. In mutation breeding, the researchers exposed
an ecotype (or variety) of A. thaliana (ecotype Columbia) to a chemical,
ethyl methanesulphonate, that induces mutations in genes. They then isolated
individuals that had a mutant version of the allele coding for the enzyme
acetolactate synthase (Csr1-1) which conferred resistance to chlorsulphuron.
They isolated those individuals (by spraying the plants with chlorsulphuron;
only the resistant ones survived) and backcrossed them to wild-type A.
thaliana ecotype Columbia for six generations. For the GE plants, they
inserted the Csr1-1 gene using a certain vector and created two separate GE
lines, i.e. two separate transformation events. Each line contained
insertions of the Csr1-1 transgene at a single site.

A. thaliana is normally a self-pollinating species with very low rates of
cross-pollination. Thus, it was thought that there would be virtually no
gene flow to other individual A. thaliana plants and thus virtually no risk
of transgenes moving from engineered A. thaliana to non-engineered
neighbors. There were also questions as to whether there were any ecological
differences between conventional breeding and GE versions. An experiment was
designed to test these issues. The experiment entailed planting 144
plants-of which 25% were wild type, 25% contained the HT gene via mutation
breeding, and 50% contained the HT gene via GE (25% from line 1 and 25% from
line 2)-and then collecting about 100,000 seeds from the wild-type plants
and looking to see how many carried the HT gene, i.e. to look at the
per-plant outcrossing rate.

The results were quite surprising. The per-plant outcrossing rate was 0.30%
for mutant fathers (i.e. containing the HT gene from mutation breeding) and
5.98% for transgenic fathers (i.e. containing the HT gene from GE). Thus,
transgenic A. thaliana were 20-fold more likely, on average, to outcross
than ordinary mutants (i.e. those derived from mutation breeding). Further
genetic investigation found that the outcrossing rates in the two GE lines
were very different-1.2% and 10.8%. Thus, the two GE lines of A. thaliana
demonstrated 4-fold and 36-fold higher rates of outcrossing compared to
traditional breeding. Since the HT gene was the same, the differences
between GE and mutation breeding appear to be associated with the overall
process of genetic engineering. The differences between the two GE lines
appears to be due to the difference in location as to where the insertions
happened, as the entire genetic construct was the same. This experiment
clearly shows that a difference exists between conventional (including
mutation) breeding and genetic engineering. In essence, in the one GE line,
the act of genetic engineering had transformed a species that was normally
an inbreeder to an out-crosser.

Another example of an unexpected effect that may have been due to the
location of the insertion occurred in an experiment with yeast that involved
adding not a transgene from another species but inserting multiple copies of
a naturally occurring yeast gene. In that experiment, the scientists found
that a three-fold increase in an enzyme in the glycolytic pathway,
phosphofructokinase, resulted in a 40-fold to 200-fold increase of
methyglyoxal (MG), a toxic substance which is known to be mutagenic,
depending on the yeast line. As the scientists themselves concluded, "the
results presented here indicate that, in genetically engineered yeast cells,
the metabolism is significantly disturbed by the introduced genes or their
gene products and the disturbance brings about the accumulation of the
unwanted toxic compound MG in cells. Such accumulation of highly reactive MG
may cause a damage in DNA" (Inose and Murata, 1995). The position of the
insertion could potentially explain why the same genetic construct caused
from a 40-fold to 200-fold increase in MG concentration, depending on the
different yeast transformation events.

Use of vectors designed to move and express genes across species and
ecological barriers
............................................................................
............................................................

A third important way genetic engineering differs from conventional breeding
is in its introduction of genes that move and cause expression of desired
traits.

Since traditional (or conventional) breeding involves mixing of genetic
material from species that are sexually compatible/fertile, there is no need
for special genetic elements to facilitate this process; sexually compatible
species already contain such elements. The same is not true with GE, which
utilizes non-sexual means of reproduction and usually entails the movement
of genetic material between species that could rarely, or never, exchange
genetic material in natural conditions. To facilitate this process, GE makes
use of vectors specifically designed to move and express genes across
species and ecological barriers. These vectors consist of genetic elements
and sequences derived from efficient genetic parasites (viruses, plasmids,
mobile elements, etc.) and are specifically designed to breach species
barriers, i.e. to smuggle genes into cells that would otherwise exclude them
and get the genetic material inserted into the genome of the host plant.

In microorganisms, plasmids are known to move readily between bacteria. In
crop genetic engineering, plasmids are invariably used and are derived from
the tumor-inducing plasmid (the Ti-plasmid) of the bacterium Agrobacterium,
as discussed earlier.

Genetic elements from Agrobacterium are never added to a plant's DNA through
conventional breeding, and are only see in the DNA of other species in
nature in plants infected with crown gall or hairy root disease, in the
infected cells.

Virtually all crop plants derived via GE also contain a powerful promoter (a
genetic regulatory or "on"-switch) from the Cauliflower mosaic virus (the
CaMV 35S promoter), which in nature causes a disease in plants in the
mustard family. Normally, genes in a plant have their own promoters so that
the gene will be turned on at the right time in development and will be
expressed at the right level, i.e. the right amount of the desired gene
product will be produced. A promoter from a plant virus is used because
viruses are genetic parasites that have the capability to infect a plant
cell and hi-jack its cellular machinery to make multiple copies of itself in
a short period of time. The CaMV 35S promoter is used precisely because it
is such a powerful promoter, which leads to hyperexpression of the
transgenes, having them be expressed at perhaps 2 to 3 orders of magnitude
higher than of the organism's own genes. The CaMV 35S promoter effectively
puts the transgene(s) outside of virtually any regulatory control by the
host genome as the natural plant promoters for each gene allow.

Thus, the use of a foreign promoter is needed in GE and is not found in
traditional breeding, including hybridization and wide crosses and so
constitutes a difference between GE and conventional breeding. Indeed, for
most of the genes that are being transferred (gene for herbicide tolerance,
gene for Bt endotoxin), if one used the naturally occurring promoter for
that gene, the plant would never be able to recognize the inserted gene and
express it. Thus, a promoter that works in plants must be used; hence the
reason for the widespread use of a plant viral promoter. Most promoters that
work in plants fail to get the gene expressed at a high-enough level to do
the work; hence the use of the CaMV 35S promoter (the strongest of the
various promoter in the CaMV).

Use of such strong promoters also raise safety concerns. Since the CaMV 35S
is so strong, not only can it affect the introduced transgenes, it can also
affect genes (either turn them "on" or turn them "off") thousands of base
pairs upstream and downstream from the insertion site on a given chromosome
and even affect behavior of genes on other chromosomes. Consequently,
depending on the insertion site, a gene that codes for a toxin could be
turned "on," leading to production of that toxin.

The potential of CaMV to turn genes "on" is of particular concern because of
what we are learning about how plants normally turn many genes "off,"
through a phenomenon known as gene silencing. Gene silencing appears to be a
key defense against intrusion of foreign DNA, particularly from
disease-causing organisms, and also regulates normal gene expression. In the
last 5-10 years, scientists have come to realize that genetic material can
in fact move between organisms that are incapable of mating with each other.
Such lateral movement of genetic material is called horizontal gene flow
(vertical gene flow is the movement of genes from parent to offspring), and
occurs in nature more frequently than has been assumed. Such horizontal gene
flow is know to occur in microorganisms; indeed, it is one of the main ways
that antibiotic resistance or pathogenicity is passed around among bacteria.
Furthermore, numerous viruses can insert themselves into host genomes.

Until recently, such horizontal gene flow was considered rare or
non-existent in plants. In 1998, scientists reported evidence that genes
from a fungus had invaded 48 out of 335 genera of land plants surveyed and
that such movement occurred on some 32 separate occasions (Cho et al.,
1998). They extrapolated these genes had invaded higher plants via
horizontal transfer over 1,000 times and that such a "massive wave of
lateral transfers is of entirely recent occurrence" (Cho et al., 1998:
14244). Just a couple of months ago, a paper in the November 19, 1999 issue
of the Proceedings of the National Academy of Sciences demonstrated that
sequences from a previously unidentified tobacco pararetrovirus had
repeatedly integrated themselves into tobacco chromosomes (Jakowitsch et
al., 1999). Prior to this study, plant viral sequences were thought to
integrate rarely, if at all, into host genomes.

The recognition that genetic material can move laterally between species,
along with the recognition in recent years that DNA is not as fragile as
previously thought and can persist for extended periods of time in a variety
of habitats-aquatic, terrestrial, etc.-has lead to increasing research on
the mechanisms that organisms use to prevent the intrusion of foreign DNA.
After all, since genomes are complexly regulated wholes, work with other
complex systems has shown that intrusion of new elements can lead to
destabilization of that whole. Indeed, normal development in a plant
requires an exquisite coordination of genes, with the right set being turned
on at the proper moment in development. The plant's regulatory system should
have a mechanism to ensure that unwanted disruptions of such an elaborately
coordinated system are prevented or minimized.

Such defenses have been found to exist, and consist of pre-integration and
post-integration (i.e. before and after the foreign DNA has been
incorporated into the host chromosome) mechanisms (Traavik, 1998). The
pre-integration mechanisms include preventing the DNA from entering the cell
or digesting the foreign DNA (with nucleases) that enters the cell.

The post-integration mechanisms consist of forms of "gene silencing." Gene
silencing was initially discovered in transgenic plants and was initially
thought to occur only in the case of transgenes. It is a significant
impediment to genetic engineering because it leads to instability. A review
of this topic in 1994 stated this succinctly: "While there are some examples
of plants which show stable expression of a transgene these may prove to be
the exceptions to the rule. In an informal survey of over 30 companies
involved in the commercialization of transgenic crop plants, which we
carried out for the purpose of this review, almost all of the respondents
indicated that they had observed some level of transgene inactivation. Many
respondents indicated that most cases of transgene inactivation never reach
the literature" italics added (Finnegan and McElroy, 1994: 883).

Gene silencing can occur by preventing either transcription (making a
messenger RNA [mRNA] copy of a DNA sequence) or translation (making a
protein from the mRNA); the former occurs in the nucleus, the latter in the
cytoplasm. Hypermethylation of genetic material is one mechanism associated
with preventing transcription (Matzke and Matzke, 1995) while formation of
aberrant RNA molecules, with occasional DNA methylation, is the main
mechanism for posttranscriptional silencing (Scheid et al, 1998).

Indeed, transgene silencing is becoming a frequently observed phenomenon.
Although not completely understood, a number of factors have been shown to
affect transgene inactivation including insertion of multiple copies of the
transgene, hyperexpression of transgenes (e.g. due to use of CaMV 35S
promoter) and environmental factors (Srivastava et al., 1999). High numbers
of copies of the transgene and presence of multiple insertion sites lead to
a much higher incidence of gene instability. Since these are characteristics
of direct gene transfer methods, which are commonly used on cereals, we
should expect a higher probability of problems in such crops.

Perhaps the first, and most well studied, example of such unstable transgene
silencing was seen in work done in Germany with petunias that were
engineered with a single gene from corn to produce a new salmon red flower
color (Meyer et al., 1992). After transforming the petunias, the scientists
worked with a line that contained a single copy of the inserted gene at a
single insertion site (i.e. the most stable situation). Some 30,000
transgenic petunias carrying a single gene conferring the salmon red flower
color phenotype were grown outside and observed for differences. Initially,
the scientists were looking for mobile elements (so-called "jumping genes"
or transposons) that were naturally occurring-such mobile elements would
"jump" into the color gene disrupting it and leading to a different
color-and thought to occur at frequencies of 1 in a 100 to 1 in 100,000. The
unexpected result was the finding that significant numbers of the plants
were either weakly colored, white, had variegated colors or different
sectors of the flower being different colors. Since petunias produce up to
50 flowers over the course of the growing season, any changes in individual
plants can be easily seen. Furthermore, the number of non-salmon red flowers
increased during the season. At the beginning of the season, the percentage
of flowers with various color patterns were as follows: salmon red, 91.6%,
weakly colored, 7.6%, sectored colored, 0.3%, variegated, 0.2%, and white,
0.3%. By the end of the season the figures were 37.6%, 60.9%, 1.1%, 0.2% and
0.2%, respectively. The change in color was linked both to the age of the
plant and to environmental circumstances as well-there was a three-week
period near the end of the growing season with particularly hot days and
bright sun. Analysis at the molecular level revealed that the bulk of the
non-salmon red flowers exhibited methylation of the promoter (which was the
CaMV 35S) associated with the transgene.

This result, which was quite unexpected, clearly demonstrates that the
transgene are unstable and prone to being switched off or turned down. It
also demonstrates the important effect of the environment as the flower
color changed over time; by the end of the season over 62% of the flowers no
longer exhibited the full salmon red color. Thus, there appears to be
greater instability in the transgene expression over time, depending on both
the age of the plant and environmental conditions.

Since this study, more work on gene silencing has been done. The newer work
has also shown that "gene silencing" is not restricted to transgenes, but is
found to occur naturally under certain conditions. The current scientific
thinking is that gene silencing evolved for three purposes: to regulate
normal gene expression; to inactivate foreign DNA that comes from pathogens;
and to prevent genetic events-such as movement of "jumping genes"
(transposons)-which may disrupt the normal structure and function of the
genome. In an overall sense, gene silencing serves to protect a genome from
being disrupted by external or internal forces. Since it serves as a
mechanism for detecting and destroying foreign genetic material, it's not
surprising that gene silencing happens so frequently in GE. Thus, for GE to
work, the genetic engineer must use all sorts of mechanisms to attempt to
overcome the plant's natural defenses. That's the reason for the use of
powerful genetic elements from viruses (promoters and enhancers), pathogenic
bacteria, and mobile elements (e.g. transposons).

Given the inherent unstability of transgenes and the phenomenon of gene
silencing, which can be influenced by environmental conditions, we would
expect to see problems associated with transgene stability in the field. The
unpredictable influence of the environment may explain what went wrong in
Missouri and Texas with thousands of acres of Monsanto's glyphosate tolerant
cotton and Bt cotton, respectively. In Missouri, in the first year of
approval, almost 20,000 acres of this cotton in malfunctioned. In some cases
the plants dropped their cotton bolls, in others the tolerance genes were
not properly expressed, so that the GE plants were killed by the herbicide
(Fox, 1997). Monsanto maintained that the malfunctioning (a result of gene
unstability) was due to "extreme climatic conditions." A number of farmers
sued and Monsanto ended up paying millions of dollars in out-of-court
settlements. In Texas, a number of farmers had problems with the Bt cotton
in the first year of planting. In up to 50% of the acreage, the Bt cotton
failed to provide complete control (a so-called "high dose") to the cotton
bollworm (Helicoverpa zea). In addition, numerous farmers had problems with
germination, uneven growth, lower yield and other problems. The problems
were widespread enough that the farmers filed a class action against
Monsanto. Just a few months ago, Monsanto settled the case out of court,
again by paying the farmers a significant sum (Schanks [plaintiffs
attorney], personal communication).

Horizontal gene flow is the closest thing to genetic engineering in nature.
However it appears that only a limited number of microorganisms can insert
DNA into plants, and that plants have evolved defenses against this.
Further, each insertion is a one-time event, whereas with GE, rather than a
single mutant individual appearing, the environment is flooded with many
many transformed plants, containing DNA from sources that bacteria would
never naturally carry. Again, GE is a quantum leap from the natural
phenomenon. The simultaneous introduction of the CaMV promoter gene, to
override silencing, destanbilizes the engineered genome

Another significant differences between conventional breeding and GE is the
virtually ubiquitous use of marker genes that code for antibiotic
resistance. Such marker genes are needed to facilitate identification of the
fairly rare cases where genetic transformation has been successful. The
widespread use of genes that code for resistance to antibiotics raise the
potential question as to whether such genes be horizontally transferred to
bacteria rendering them resistant to the antibiotic in question.

Conclusion
................

Genetic engineering clearly differs from conventional breeding in several
ways. Conventional breeding relies primarily on selection, using natural
processes of sexual and asexual reproduction. Genetic engineering utilizes a
process of insertion of genetic material, via a gene gun or other direct
gene introduction methods, or by a specially designed bacterial truck, which
does not occur in nature. Genetic engineering can insert genetic material
from any life form into any other; conventional breeding generally can only
work within a species, or at most, within closely related genera, as when
they do wide crosses. Conventional breeding relies on mixing characteristics
from different populations within a species and then selecting from a plants
natural complement of genetic elements. However genetic engineering relies
on inserting genetic elements, and they end up in random locations, which
can disrupt complex gene interactions. Many of the products exhibit
unexpected effects.

Genetically engineered plants almost always contain a viral promoter gene,
the "on"switch for the gene inserted; genetic material from Agrobacterium,
which facilitates transfer of the genetic construct into a plant's genome;
and in most cases a bacterial antibiotic marker gene. These are never
deliberately introduced in products of conventional breeding.

There are thus key identifiable scientifically documentable differences
between genetic engineering and conventional breeding, both in the process,
and in the genetic makeup of the product. Indeed, in any situation in which
DNA is recoverable, the presence of engineered DNA can be identified in the
product.

Whether these differences are "significant" or "insignificant", however, is
a value question and a philosophical question, not a scientific question. We
see genetic engineering as a quantum leap from conventional breeding-as
different from it as nuclear power generation is from a coal-fired plant. In
our view traditional breeding is humankind's attempt to manipulate natural
breeding processes for our own benefit. But this attempt, while wildly
successful in one sense (the creation of all the major crop plants from
weedy wild relatives), has only mildly pushed the barriers of genetic
material transfer. GE, on the other hand, does away with all such barriers
in the natural world, permitting scientists to manipulate genetic materials
in a way that was inconceivable before.

A number of scientists, particularly ecologists, see the differences as we
do. However other scientists, particularly molecular biologists maintain it
is a continuum. In the end, it is a matter of values, judgment and opinion
as to who is correct. While science can inform this debate, this is not a
question science can answer. Indeed, it can well be argued that there is no
one right answer as to whether this difference is "significant" or not.

In terms of a FDA decision about labeling, this debate about how
"significant" the difference is should be irrelevant. If there is a
documentable difference between two foods, or two processes, and consumers
care about the difference, then under the Food Drug and Cosmetic Act FDA has
the authority to require labeling and should do so. It does not matter if it
is a small difference or a large difference. Nor does it matter whether
consumers are "right" or "wrong" to care about this difference.

Labeling would not be a deviation from previous FDA policy. Indeed, the
failure to require labeling is a deviation from previous FDA policy. The
difference between frozen peas and fresh peas, one could easily argue, is
much less than the difference between genetically engineered peas and
conventional peas. The frozen and fresh peas can be genetically identical.
The frozen peas may even be nutritionally superior, even as consumers choose
fresh peas thinking fresh is better. Yet FDA appropriately requires labeling
about the difference, and allow consumers to make their own choices about
what to buy, even if those choices are a "mistake", leaving it to the
marketplace to educate consumers about pluses and minuses of each type of
product. It should do the same for any food produced by, or derived from
food produced by, a process that inserts genetic material using a gene gun,
a specially-designed vector, or a comparable method.

Additional reasons to label include helping consumers manage food allergies
and sensitivities and allowing the public health community to track and
identify any unexpected effects. These are discussed in more detail in
Consumers Union's comments to FDA on Docket No. 99N-4282.

The science is also clear that this unique and identifiable process of
genetic engineering creates a new and unique potential for unexpected
effects, due to the unique nature of the material being inserted, from a
genome which has not previously interacted with the host genome, due to lack
of control over the location at which the gene is inserted, and due to the
introduction the CaMV "promoter" gene, which overrides the existing genetic
programming. FDA therefore has an obligation to require mandatory reviews of
all genetically engineered food before it goes on the market, and develop
ways to screen for unexpected effects which could have health consequences.

There are also predictable risks, such as potential risks of toxins,
allergens and nutritional changes and antibiotic market genes, which FDA
should address. These are discussed further in our comments to the docket.

The details of what that safety review entails should be developed through a
further process of notice and comment.

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** NOTICE: In accordance with Title 17 U.S.C. Section 107, this material is
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Last Updated on 2/17/00
By Rachel C. Benbrook
Email: karen@biotech-info.net