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Date:

August 7, 2000

Subject:

Agnet Aug. 8/00

 

AGNET AUGUST 8, 2000

Australian agency draft clears 2 new GMO cotton varieties
Anti capitalism anti ag biotech groups are organizing protest actions
against the Cambridge Healthtech Institute¹s August 20 - 22
ABC to correct report that challenged benefits of organic foods
Safety fears temper support for GMOs
Hybridizing with the enemy
New technology helps explain stream sediment movement
Genetically modified plants and the 35S promote


Agnet is produced by the Centre for Safe Food at the University of Guelph
and is sponsored by the Ontario Ministry of Agriculture, Food and Rural
Affairs Plants Program at the University of Guelph, with additional support
provided by the U.S. National Pork Producers Council, the U.S. National Food
Processors Association, Ag-West Biotech, Novartis Seeds, AGCare
(Agricultural Groups Concerned About Resources and the Environment),
Monsanto Canada, Pioneer Hi-Bred Limited (Canada), Ontario Egg Producers,
U.S. National Cattlemen's Beef Association, Ontario Agri-Food Technologies,
Novartis Crop Protection Canada, Halton Regional Health Department, the
Rutgers Food Risk Analysis Initiative, the Crop Protection Institute,
Agriculture and Agri-Food Canada, Ontario Corn Producers Association,
Capital Health, Plant Protection Branch Dept of Agriculture Fisheries
Forestry Australia, Performance Plants, Cargill AgHorizons, the Ontario
Soybean Growers Marketing Board, the Canadian Cattlemen's Association,
AdCulture, Food Industry Environmental Network, Dow AgroSciences, W.G.
Thompson & Sons, Crop and Food Research New Zealand, and the Agricultural
Adaptation Council (CanAdapt Program).

archived at:
http://www.plant.uoguelph.ca/safefood/archives/agnet-archives.htm



AUSTRALIAN AGENCY DRAFT CLEARS 2 NEW GMO COTTON VARIETIES
August 8, 2000
Dow Jones
Ray Brindal
CANBERRA --Australia¹s gene technology regulator has, according to this
story, given preliminary approval for the general use of two genetically
modified varieties of cotton proposed by Monsanto Australia Ltd., a unit of
U.S.-based drug giant Pharmacia Corp. (PHA).
The two new varieties are Roundup Ready cotton and Roundup Ready/Ingard
cotton.
The story says that the government¹s Genetic Manipulation Advisory Committee
assessed the biosafety of the two varieties and reported its findings to the
government¹s Interim Office of the Gene Technology Regulator.
The technology regulator was quoted as saying in statement issued Friday
that, "GMAC considers that general release of Roundup Ready cotton would
pose no additional risk to human health and safety or to the environment
arising from the genetic manipulation of this cotton."
But it considered there were risks that could result from inappropriate
management of the crop-herbicide Roundup combination.
It said any release of the new product should be done with an appropriate
crop management plan to minimize the potential for adverse effects.





ANTI CAPITALISM ANTI AG BIOTECH GROUPS ARE ORGANIZING PROTEST ACTIONS
AGAINST THE CAMBRIDGE HEALTHTECH INSTITUTE¹S AUGUST 20 - 22
August 8, 2000
from an Internet statement
http://www.tao.ca/~ban/grainrage.htm
For information about the Organic Consumers Association go to the
following www site: http://www.purefood.org/
For information about activist previous actions, including vandalism,
go to the following www site: http://www.tao.ca/~ban/ar.htm

The Mad scientists are returning to Minneapolis !
On Aug 20,21,22 a biotechnology conference will be taking place at
Minneapolis
Marriott City Center 30 South Seventh Street.
Less than 2 weeks after the successful anti-ISAG demonstrations, we have
another oppurtunnity to raise a collective call of NO! to the biotech
industry and researchers, and to show the powers of the state that we have
not been weakened by their attacks upon us! Some speakers include Dr. Bill
Timberlake, Monsanto Corporation, Dr. Ralph Scorza, U.S. Department of
Agriculture, and Dr. David A. Somers, University of Minnesota ( the oat guy)
and topics include-Improving the Feed Value of Corn, Engineering More
Efficient Photosynthesis, and Therapeutic Proteins from Transgenic Corn, to
name a few. the web site for the conference
http://www.healthtech.com/conference/00crp/
We are asking for endorsments for the following call to action against
biotech
and global capitalism.
Email tom@organicconsumers.org to sign on as endorsers.
--
CALL TO ACTION AGAINST BIOTECHNOLOGY!!
SUNDAY AUGUST 20-7:30 PM LORING PARK-SPEAK OUT AGAINST BIOTECHNOLOGY AND
POLICE BRUTALITY. A CANDLELIGHT VIGIL AND MARCH TO THE CONFERENCE SITE WILL
FOLLOW.
MONDAY AUGUST 21 RALLY AT THE CONFERENCE SITE/AUTONOMOUS ACTIONS
Help is needed here on some wording !!!!!! Lets talk against biotech, police
oppression for isag, global capital and tie it all together. lets encourage
people to organize themselves so we can avoid any "organizational" mettings,
which i dont see any point to. lets also ask people who want to speak sun to
let you know in advance
lets think of other folx to pass this around to for endorsment./get back to
me
Endorsed by:
GrainRAGE
ORGANIC CONSUMERS ASSOCIATION
MN NORML
CITIZENS LEAGUE OF @NTI-CIVILIZATION VOTERS





ABC TO CORRECT REPORT THAT CHALLENGED BENEFITS
OF ORGANIC FOODS
August 8, 2000
N.Y. Times/AP
http://www.nytimes.com/yr/mo/day/news/financial/abc-2020.html
ABC News was cited as saying yesterday that a report challenging the assumed
benefits of organic food was partly based on research that did not exist and
that
it would make a correction on Friday night¹s "20/20" program.
In the report, the correspondent John Stossel said research commissioned by
ABC News showed that conventional produce did not necessarily have more
pesticide residue than did organic produce.
"Our tests, surprisingly, found no pesticide residue on the conventional
samples or the organic," he said in the report first broadcast on Feb. 8 and
again on July 7.
But the two researchers who were commissioned to do the testing -- Dr.
Michael Doyle, a scientist with the University of Georgia, and Dr. Lester
Crawford, director of the Center for Food and Nutrition Policy at
Georgetown University -- said they had never tested produce for pesticide
residue for ABC.
In a statement released last night, ABC was cited as confirming that
pesticide tests were never performed on produce. But it steered blame away
from Mr. Stossel, adding, "In making that statement, Mr. Stossel was relying
on inaccurate information that had been provided to him."
Executives said David Fitzpatrick, producer of the segment, was responsible
for the error, and they were trying to determine how it appeared. But, they
said, they believed it was an honest mistake and did not think Mr.
Fitzpatrick
would be disciplined. Mr. Stossel will make the correction.
The stories note that problems with the report were first brought to light
by the members of the Environmental Working Group, which supports the
consumption of organic food. They had learned that Mr. Stossel¹s assertion
about the pesticide tests was in error after speaking with the researchers.
They apprised Mr. Stossel of their findings in a letter dated Feb. 8. They
were answered by Mr. Fitzpatrick, who, in a letter, asserted that ABC did,
indeed, test produce for pesticide residue. After the report was rerun, Mr.
Stossel re-emphasized the pesticide assertion in an on-the-air conversation
with Cynthia McFadden, a "20/20" anchor.
Executives at ABC, a unit of Walt Disney, said they were trying to determine
why the group¹s assertion about the supposed pesticide tests was not
properly
addressed when it was first raised.
The Environmental Working Group also contended that Mr. Stossel¹s report
had inappropriately implied that ABC¹s tests had detected dangerous strains
of E. coli bacteria in the organic food when, in fact, the tests did not
establish the presence of the dangerous type of E. coli.
Executives said they were still looking into that accusation.
Kenneth Cook, president of the Environmental Working Group, was cited as
saying that he was not satisfied with ABC¹s statement, stating, about
Stossel, "He¹s not a contrarian, he¹s a counterfeiter who¹ll do anything for
ratings. He needs to be fired."




SAFETY FEARS TEMPER SUPPORT FOR GMOS: BRITISH COLUMBIANS, WHO ARE GUNG-HO
FOR SOME USES OF BIO-ENGINEERED CROPS BUT LESS SO FOR OTHERS, ARE RIGHT TO
INSIST ON VIGILANT TESTING AND CONTROL OF NEW PRODUCTS.
August 8, 2000
The Vancouver Sun
Editorial
A10
While the debate over genetically modified food was reaching hysterical
levels in Europe and inciting riots in North America, the Pollara research
company in Toronto was, according to this editorial, sifting poll results
and reckoning the level of concern among Canadians.
They found some surprises. First, most Canadians have a pragmatic attitude
towards bio-engineering‹acknowledging its potential for good, aware there
may be yet unknown ills, but willing to take informed risks.
The survey was done for the federal government to determine what Canadians
know about the subject and what they want to know.
British Columbians are more negative about biotechnology than other
Canadians; one in four people in the B.C. focus groups opposed it compared
to fewer than one in five elsewhere. That is perhaps because, says
government spokesman Roy Atkinson, British Columbians tended to be more
aware of the biotech industry, and "with awareness they begin to
discriminate between different applications, and they have more questions.¹¹
The editorial says that one reason for that awareness is that B.C. has more
than 80 bio-tech companies as well as the public-private Genome Sequence
Centre, and the province is home to Nobel Prize-winning biochemist Michael
Smith. The industry is on course to become the province¹s second biggest
technology industry.
B.C. participants were gung-ho for biotech in medical applications (or
"pharming¹¹ as it¹s called) and in instances where the result is beneficial
to the environment, as in pest-resistant plant strains that reduce the use
of pesticides.
They were less approving of its use to simply increase crop yields or bring
prices down. They judged that as unnecessary, which says more about the
abundant, cheap food we enjoy in our neck of the global woods than it does
about the benefits of drought-proof rice and wheat elsewhere in the world.
As in other parts of Canada, B.C. residents insisted on vigilant testing and
control of new genetically modified products‹something Mr. Atkinson points
out the government has begun to address with some $90 million in new funds
for GMO administration and regulation in the last budget.
This is what we need to hear. Canada has been a leader in bio-engineered
foodstuffs. It would be a fine idea if we were also a leader in proving them
safe.



HYBRIDIZING WITH THE ENEMY
August 7, 2000
Science Now
Mari N. Jensen
http://sciencenow.sciencemag.org/cgi/content/full/2000/807/2
SNOWBIRD, UTAH‹An exotic species of cordgrass is, according to this story,
driving a native one out of existence in San Francisco Bay‹not just by
outcompeting it for light, water, nutrients, or space directly, like most
invasive species, but also by letting hybrids do the dirty work.
The story says that cross-pollination between the two species is rare,
researchers reported here on 6 August at the annual meeting of the
Ecological Society of America, but once it happens, the resulting hybrids
mate much more readily with the natives, enabling them to take over the
population quickly.
The fast-growing grass Spartina alterniflora, a native of the eastern United
States, was deliberately introduced to three salt marshes in San Francisco
Bay in the mid-1970s.
Now, the less hardy native cordgrass S. foliosa has been crowded out of many
tidal creeks and channels on the southern side of the bay‹not just by S.
alterniflora, but also by hybrids between the two species. "The amount of
hybridization surprised us all," says Debra Ayres, an ecologist at the
University of California, Davis. The results have been
devastating: Sparsely vegetated mudflats that used to host thousands of
migrating shorebirds have been replaced by densely vegetated meadows of
2-meter-tall S. alterniflora and its hybrids.





NEW TECHNOLOGY HELPS EXPLAIN STREAM SEDIMENT MOVEMENT
August 8, 2000
ARS News Service
Agricultural Research Service, USDA
New technology is helping scientists demystify erosion dynamics along stream
channels in agricultural watersheds.
Agricultural Research Service hydraulic engineer Roger Kuhnle and hydraulic
technician John Cox at the National Sedimentation Laboratory in Oxford,
Miss., tested an acoustic device called the SedBed Monitor. They used it to
measure the rate of sediment movement by measuring the size and speed of
dunes that migrate along the bottom of streams. The device was developed by
researchers at the University of Mississippi¹s National Center for Physical
Acoustics, in cooperation with Kuhnle.
After lab-testing the SedBed Monitor for several years, Kuhnle field-tested
a modified version at Goodwin Creek watershed in northern Mississippi for
three years during 12 heavy rains that produced runoff. A special microphone
picks up sound that bounces off sediment as it moves along the stream
bottom. The data automatically feeds into a computer that only operates when
the stream¹s water depth is above a minimum level.
Kuhnle uses the size and migration rate of the dunes from the records, along
with the dune density, to calculate the rate of sediment movement in the
test channel. Obtaining this information using conventional sampling methods
would take hours because sediment movement is so variable.
For channels in agricultural and other watersheds to remain stable, the
amount of sediment moving into the channel must equal the sediment moving
out. The roughness of the stream bottom plays a key role in this sediment
movement‹and this information hasn¹t often been available for streams that
contain sand and gravel.
This technology will help researchers refine and improve current flow and
sediment rate prediction methods. It¹s also critical to engineers in the
U.S. Army Corp of Engineers and U.S. Department of Agriculture¹s Natural
Resources Conservation Service responsible for the ecological and
environmental stability of watershed drainage systems. ARS is the USDA¹s
chief research agency.





GENETICALLY MODIFIED PLANTS AND THE 35S PROMOTER: ASSESSING THE RISKS AND
ENHANCING THE DEBATE; DEBATE 2000¹0802 A: ROGER HULL, S.N. COVEY AND PHIL
DALE ON THE 35S DEBATE R. HULL, S.N. COVEY AND P. DALE JOHN INNES CENTRE,
NORWICH RESEARCH PARK, COLNEY, NORWICH NR4 7UH
August 7, 2000
From: Klaus Ammann Dear friends, here another rebuttal to Mae van Ho¹s article, placed in the
same journal, Microb. Ecol. Health Dis.
thanks, Roger (roger.hull@bbsrc.ac.uk) for sending this piece, it sure
enhances the quality of the debate about the 35S promoter
Klaus
R. Hull, S.N. Covey and P. Dale
John Innes Centre, Norwich Research Park, Colney, Norwich NR4 7UH, UK
Abstract
The 35S promoter, derived from the common plant virus, cauliflower mosaic
virus (CaMV), is a component of transgenic constructs in more than 80% of
genetically modified (GM) plants. Alarming reports have suggested that the
35S promoter might cause accidental activation of plant genes or endogenous
viruses, promote horizontal gene transfer, or might even recombine with
mammalian viruses such as HIV, with unexpected consequences. In this
article, we discuss the properties of CaMV and the 35S promoter and the
potential risks associated with the use of the promoter in GM plants,
concluding that any risks are no greater than those encountered in
conventional plant breeding.
--
Introduction
In a recent article, Ho et al. (1999) suggested that the widespread use of
the 35S promoter of cauliflower mosaic virus (CaMV) in transgenic plants is
"a recipe for disaster". Ho et al. (1999) base their arguments on three
considerations, a) that the CaMV 35S promoter has a hotspot for
recombination (Kohli et al., 1999); b) that the 35S promoter has several
domains with different tissue specificities and c) that the 35S promoter is
very efficient and can function in a wide range of organisms, not only
plants but also bacteria and animals. From this they deduce that the 35S
promoter could recombine to activate dormant viruses, create new viruses and
"cause cancer by the overexpression of normal genes". As scientists who
have worked on CaMV for up to 25 years and have contributed much to the
understanding of its molecular biology we wish to put these scenarios in the
correct context.
The first plant promoter
Over 15 years ago, CaMV was one of several plant genetic systems being
studied for its potential use in plant transformation (Hull, 1983; 1984;
1985). As part of these studies, much basic research went on into
understanding the genetic organisation of CaMV and the means by which its
genes are expressed and regulated. The CaMV genome was the first
significant piece of plant DNA to be completely sequenced (Frank et al.,
1980) and the two CaMV promoters, the 35S and 19S promoters, were the first
plant promoters identified (Covey et al., 1981; Hull and Covey, 1983c; Odell
et al., 1995). Because of the latter discovery, and the finding that the 35S
promoter was active in directing heterologous expression of plant genes in a
variety of plants, its use in the development of GM plants for research and
agronomic applications became widespread.
The virus
CaMV can infect a wide range of crucifers (see Schoelz and Bourque, 1999)
and is commonly found in cabbages, cauliflowers, oilseed rape, mustard and
other brassicas in temperate countries (Tomlinson, 1987). A survey of a
local market, as part of a risk assessment exercise for the Ministry of
Agriculture, Fisheries and Food (the UK regulatory authority for biosafety
of genetic manipulation of plant pests) in the late 1980s, showed that about
10% of the cauliflowers and cabbages were infected with CaMV. The virus is
transmitted in nature by aphids (see Schoelz and Bourque, 1999) and it might
be expected that organically grown crucifers, on which the aphids have not
been controlled by insecticides, would have higher rates of infection.
Infection early in the plant growth might affect the quality, especially of
cauliflowers, but later infections show leaf symptoms but little other overt
effects. The virus infects most cells of the plant and produces about 105
particles per cell. Each particle contains one molecule of the viral
genome, an 8 kbp circular double-stranded DNA with one copy each of the two
promoters.
The replication cycle of the virus has two phases (see Hohn, 1999), the
first in the nucleus where the viral genome is uncoated, forms a
minichromosome and is transcribed to give two RNA species, the 35S RNA
(using the 35S promoter) and the 19S RNA (using another promoter). These
RNAs pass to the cytoplasm where the 35S RNA acts as a template for reverse
transcription as well as a template for translation of some gene products;
the 19S RNA is the template for the translation of just one gene product.
Various unencapsidated replication intermediates are found in infected cells
(Hull and Covey, 1983a) which are estimated to give a further 104 CaMV
molecules per cell. CaMV was the first plant virus shown to involve
reverse transcription in its replication (Hull and Covey, 1983b; Pfeiffer
and Hohn, 1983) but has now been joined by more than a thirty other plant
viruses which have the same replication mechanism.
Reverse transcribing elements
There is a wide range of reverse transcribing elements from animals, plants,
bacteria and fungi (Hull, 1999). These elements are grouped together on
common features of replication which use the enzyme reverse transcriptase.
It is considered likely that they had a common ancestor. There are two basic
types of reverse transcribing elements. Reverse transcribing viruses express
gene products which enable them to move between hosts. These viruses fall
into two basic groups, the retroviruses which encapsidate RNA and whose
replication involves integration of the viral sequence into the host genome,
and pararetroviruses which encapsidate DNA and whose normal replication
does not involve integration of the viral sequence. In contrast,
retroelements are reverse transcribing sequences integrated into the host
genome but which do not produce gene products necessary for easy horizontal
movement between hosts.
Retroviruses
The retrovirus family comprises a large number of viruses which infect
vertebrates and cause a range of diseases including tumors, leukemia and
immunodeficiency. Retroviruses express a gene product, the integrase
protein, which facilitates the integration of the viral genome into the host
chromosomes where it can stay dormant for a considerable time. The virus
particles, which are horizontally transmitted, contain RNA transcribed from
this integrated genome. On entry into a new host this RNA is reverse
transcribed to give the DNA which is then integrated.
Plant pararetroviruses
There are two groups of plant pararetroviruses, the caulimoviruses and the
badnaviruses (Hull, 1995; Lockhart et al., 1995) (the International
Committee on Taxonomy of Viruses has a more complex classification system
but for this article it is best to consider these viruses in these two
groups). The caulimovirus group includes viruses which infect groundnuts,
soybeans and cassava as well as brassicas. Crops infected by badnaviruses
include banana, cocoa, citrus, yams, pineapple and sugarcane. Although
there are differences in genome organisation between these two virus groups
their replication and the expression of their genes are very similar. The
DNA in the virus particles is transcribed in the nucleus (using the 35S
promoter) to give RNA which is replicated by reverse transcription to form
the DNA molecules which are encapsidated in the virus particles.
Animal pararetroviruses
The one group of animal pararetroviruses, the hepadnaviruses, contains the
human-infecting hepatitis B virus and several viruses which infect ground
squirrels, woodchucks and ducks. These viruses have a very different genome
organisation to plant pararetroviruses, and although they replicate by
reverse transcription, there are major differences from retroviruses and
plant pararetroviruses in the details of the replication mechanism ( Mason
et al., 1987; compare Seeger 1999 for hepadnaviruses with Hohn, 1999 for
caulimoviruses).
Retrotransposons.
Retrotransposons are similar to animal retroviruses in that they are
integrated into the host chromosomes and their replication is by mechanisms
basically the same as those of retroviruses using a promoter analogous to
the 35S promoter. As noted above, they lack the gene products which enable
them to spread horizontally between hosts as do the retroviruses. However,
there is some recent evidence that they can move very infrequently between
hosts (Jordan et al., 1999) by an unknown mechanism. Plant genomes contain
large numbers of retrotransposons (Bennetzen and Kellog, 1997). For
instance, up to 50% of the maize genome is made up of retrotransposons
(SanMiguel et al., 1996) though many of these have mutated and are likely to
be inactive.
Relationships between reverse transcribing elements
As noted above, all these elements have a common mode of replication
involving reverse transcription of RNA to form DNA. However, functionally
reverse transcribing elements fall into two types, the retroviruses, plant
pararetroviruses and retrotransposons forming one type and the animal
pararetroviruses forming the other type. Within these types, each virus or
element is a highly coordinated structure and perturbation of the sequence
leads to loss of infectivity or functionality. This is exemplified by the
attempts to use cauliflower mosaic virus as a gene vector (see Hull, 1983).
In most cases, it is only when closely related sequences are added to or
exchanged within the genome that viability is retained.
There are many instances of plant and animal cells containing more than one
type of reverse transcribing virus or element. For instance, there are
several different human retroviruses and no instance of recombination has
been found between them. This indicates that there are many constraints on
natural recombination.
Now to consider the specific points raised by Ho et al. (1999).
1. The integrated 35S promoter can recombine with dormant viruses and also
create new viruses. We need to consider the situation firstly in plants and
then in animals which may eat those plants
For plants:
a) As noted above, there are more than 105 copies of the 35S promoter in
each cell of a plant naturally infected by CaMV, in contrast to the one to a
few copies of the 35S promoter in each cell of transformed plants. All
these other pararetroviruses have similar numbers of copies of their genomes
in their hosts but differ markedly in sequence from CaMV, even in the 35S
promoter region. Also noted above is that plants contain large numbers of
retrotransposons. In spite of these high numbers of both 35S promoter and
retrotransposons no cases of natural recombination leading to new viruses
have been found in spite of intensive research on these virus groups.
b) There is uncertainty concerning the stage of transformation at which the
recombination described by Kohli et al. (1999) occurred. They did not
distinguish between recombination taking place during the process of
transformation and recombination taking place after the sequences had been
integrated. There is accumulating evidence of rearrangements of DNA during
transformation (e.g. De Groot et al., 1994; Register et al., 1994). In most
cases, these rearrangements result in the non-functioning of the transgene
and are selected out in the early stages of analysis of the properties of
the transformed lines. Furthermore, the construct used for transformation
by Kohli et al (1999) had three copies of the 35S promoter, one in inverse
orientation in relation to the other two. The presence of repeated
sequences in transformed integrants, and especially inverse repeats, also
tends to lead to gene silencing (see Kooter et al. 1999), a condition which
would be selected against in developing the transgenic line.
c) Assuming that the integrated 35S promoter does have recombinational
properties, for it to effect the activation of a dormant virus or create a
new virus, the whole promoter would have to be either excised and reinserted
precisely at the new site or its 3¹ end linked precisely with another gene.
The first case means that there would have to be two recombination
"hotspots", that identified by Kohli et al. (1999) just downstream of the
TATA box and an upstream one which would enable the other promoter elements
to be included in the excised fragment. There is no evidence for such an
upstream "hotspot". Excision of the promoter would also be required for any
potential effects on animals.
It is important to note that genetic recombination is a normal feature of
conventional plant breeding and of all natural populations (Hayward et al.,
1993). Genetic variation is obtained by recombination following
hybridisation between genetically different plants which may be from
different species and genera. There are also irregular sources of
recombination by minor and major chromosomal rearrangements and from the
movement of transposable elements, which can move from one part of the
genome to another. Thus, recombination and hotspots for recombination are
not unique features of the CaMV 35S promoter
For animals
d) The scenario suggested here by Ho et al. (1999) is that the 35S promoter
would recombine with hepadnaviruses such as human hepatitis B virus. This
is based on the suggestion of a "close relationship between CaMV and
hepadnaviruses". Hepadnaviruses have been classed as pararetroviruses as
they have a DNA genome and they do not involve integration in their
replication cycle. However, as noted above, their replication cycle differs
significantly from that of caulimoviruses. Furthermore, there is no
sequence similarity between the "hotspot" on the CaMV 35S promoter and
hepadnavirus sequences important in replication.
e) Various problems would have to be overcome for the CaMV 35S promoter in
transgenic food plants to interact with human (or other animal) viruses or
any other sequences. Firstly, as noted above, the promoter would have to
excise in an appropriate manner. If the transgenic food was cooked the DNA
would be denatured and be very unlikely to renature in an operable form.
The next major problem is that the DNA containing the promoter would be
exposed to nucleases both from the plant cells when they were disrupted and
in the animals gut. Less than 5% administered DNA survives up to 7 hours in
an animal gut and that DNA is cleaved into very small pieces (Schubbert et
al., 1994). The DNA would then have to pass into the gut cells and
integrate precisely to activate the animal sequence. As noted above, the
consumption of CaMV-infected vegetables would result in the ingestion of
vastly more copies of the 35S promoter than the consumption of transgenic
plants containing the promoter. Brassicas are not the only crops which
contain pararetrovirus sequences. All banana varieties (and other Musa
varieties), the worlds fourth most important agricultural commodity, have
multiple copies of the sequences of banana streak badnavirus integrated into
their genomes ( Harper et al., 1999; Ndowora et al., 1999). In spite of
exposure of humans to these pararetroviruses there is no evidence of any ill
effects from them even in countries such as Uganda where bananas are the
staple diet and HIV is rife.
2. That recombination of the 35S promoter would lead to overexpression of
"normal" genes.
Once again, one has to consider both plants and animals separately.
Plants f) The same arguments apply here as those under a) - c) above.
However, if we assume that the 35S promoter does recombine to enhance the
expression of a "normal" gene leading to the plant producing a harmful
substance what are the factors to be considered? Recombination is likely
to be a very rare event and to be in one or a few cells. For it to have
any impact it would have to be in germline cells so that it could be fully
expressed in the
progeny. Also to have any impact it would have to be in an early generation
of bulking up of seed of that line. Recombination would result in the loss
of the transgenic character which would be recognised in these early
generations. By affecting a "normal" plant gene it would probably affect
the plant phenotype. Thus, the normal procedures used over many years for
the selection of new plant varieties from conventional breeding programmes
would identify this significant change.
g) Plants contain many secondary metabolites which have evolved to provide
defense mechanisms against herbivores. The standard tests for carcinogens
using rodents indicate that a significant proportion of these secondary
metabolites are "carcinogens". For instance, out of 28 tested from coffee,
19 were carcinogenic in rodents and 35 out of 63 natural plant products were
carcinogens (Ames and Gold, 1997). Since these potentially carcinogenic
compounds have not been implicated in causing human cancers, it is
considered that humans are more adapted to them. Thus, the overexpression
of normal genes is very unlikely to cause cancers
Animals
h) The same arguments as in d) and e) for the 35S promoter recombining with
an animal gene sequence also apply here. It must be remembered that animals
other than humans also eat brassicas and there are no reports of any
poisoning or disease which could be related to CaMV infection.
Conclusions
The paper by Ho et al. (1999) highlights some of the basic features of the
controversy over genetically modified crops. The transgenic situation has
to be compared with the natural situation not with a utopian one. It is
well known that viral sequences recombine naturally and that the vast
majority of these recombinants are unsuccessful. Very occasionally new
viruses arise, this being one of the major ways by which viruses evolve.
However, this recombination is between viruses which occur in plant cells at
very much higher concentrations than those of transgenic sequences, whether
they be promoters or the transgenes themselves. Furthermore, plants are
full of noxious substances which have evolved over many millenia to protect
the plant against herbivores and pathogens. Plant breeding and selection
has, and is, continuing to minimize(d) the effects that these substances
have on humans.
From the arguments above, there is no evidence that the CaMV 35S promoter
will increase the risk over those already existing from the breeding and
cultivation of conventional crops. . There is no evidence that the 35S
promoter, or other retroelement promoters, will have any direct effects, in
spite of being consumed in much larger quantities than would be from
transgenes in GM crops. Furthermore, there are compelling arguments to
support the view that there would be no more risks arising from potential
recombination than there are from existing non-transgenic crops.
--
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For more information about the Agnet research program, please contact:
Dr. Douglas Powell
dept. of plant agriculture
University of Guelph
Guelph, Ont.
N1G 2W1
tel: 519-824-4120 x2506
fax: 519-763-8933
dpowell@uoguelph.ca
http://www.plant.uoguelph.ca/safefood

archived at:
http://www.plant.uoguelph.ca/safefood/archives/agnet-archives.htm