[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
[SANET-MG] Universal Condemnation Meets UK Government’s Green Light for GM Potato Trials
ISIS Press Release 06/12/06
Universal Condemnation Meets UK Government’s Green Light for GM Potato
Trials
Assumptions of safety not justified by existing evidence
The government must withdraw permission for the trials, or the
regulators should be held responsible for any harm caused. Dr. Mae-Wan
Ho and Prof. Joe Cummins
A fully referenced version of this paper is posted on ISIS members’
website. Details here.
Big food companies reject GM potatoes and oppose the trials
The UK government has given permission to German biotech company BASF
Plant Science GmbH for the first trials of a genetically modified (GM)
crop in the country since 2003 [1]. BASF’s GM blight-resistant potato
was granted permit for field trials in Ireland earlier this year, but
the company abandoned its plans in face of strong opposition from civil
society organisations and strict conditions imposed by Ireland’s
Environmental Protection Agency [2].
The big food companies in the United States, including McDonalds,
McCains, Burger King and Pringles, had rejected GM potatoes in 2002; and
in August 2006, when BASF applied for a UK trial permit, the British
Retail Consortium said UK supermarkets would not be stocking GM potato [3].
The British Potato Council has also made its strong opposition known the
day after the government’s decision was announced [4]. It refused to
endorse the trials, and said it was paramount that public concerns were
addressed, and fears about possible cross-contamination allayed, before
trials began. The trials are to consist of five-acre plots in Derbyshire
and Cambridgeshire for five years beginning 2007, under the conditions
that the plots must be left fallow after the five-year trial so any
remaining tubers can be destroyed and none of the potatoes harvested
enters the food chain.
The GM potatoes are modified with genes from a wild Mexican relative of
potato, Solanum bulbocastanum, intended to make them resistant to the
fungus causing late blight disease; but they also have marker traits,
including herbicide resistance. BASF has not done environmental or
health impact studies on the GM potatoes [5]. In view of the growing
list of damning evidence against the safety of GM crops [6, 7] (GM Soya
Fed Rats: Stunted, Dead, or Sterile; Making the World GM-Free &
Sustainable ), approving the release of these GM potatoes is to subject
the public to serious health risks with potentially harmful effects on
wildlife. We already know that debilitating immune reactions can be
triggered by exposure to the transgenic plant, even in the case of a
single gene transfer from bean to pea, a closely related species [8, 9]
(Transgenic Pea that Made Mice Ill, SiS 29).
Late blight resistance is complex and the fungus versatile
Late blight is one of the most devastating plant diseases. It is caused
by the fungus, Phytophora infestans, a pathogen of potato and to a
lesser degree tomato. There are many genes involved in blight resistance
in potato: four main dominant genes, R1 to R4, and another seven genes,
five of which are alleles (alternative forms at the same site) of the
complex R3 locus.
Hybridisation with wild Mexican species began in 1909, and continues to
the present day. But in spite of constant efforts to create resistance,
the fungus rapidly developed strains that overcame the genetic
resistance. Chemical fungicides have been developed to control blight
but these too failed to counter the versatility of the fungus. The
fungus has two mating types (A1 and A2) both of which first appeared in
Mexico. Only the A1 mating type was present in European potatoes until
1978 when the A2 mating type appeared in Britain. The presence of the
two mating types greatly enhances gene exchange, accelerating the loss
of genetic resistance and fungicide control [10, 11].
Technology in a hurry
In the early days, resistant potatoes were obtained using true sexual
hybridisation with wild Mexican species but the resistant strains soon
succumbed to mutants of the blight fungus. A wild Mexican species,
Solanum bulbocastanum, was stably resistant to blight but could not be
sexually crossed with potatoes. A laboratory procedure of somatic
hybridisation was used to create sexual hybrids; it involves fusing
cells from cell cultures of Solanum bulbocastanum and potato, the fused
cells containing nuclei of both species. When the fused cells undergo
cell division, the chromosomes of the two species become mixed and a
single hybrid nucleus is formed in the cells. The cells can be cultured
on solid media to form a callous (tumour) which when treated with plant
growth hormones, produces plantlets that flower. The somatic hybrids
have irregular meiosis (cell division in forming germ cells during
reproduction, which reduces the chromosome number to half), with
irregular chromosome pairing and separation, but relatively stable
blight resistant lines can be obtained [12-14]. Apart from the 11
potato blight resistance genes mentioned earlier, additional genes are
involved in producing broad-spectrum resistance against blight, these
include the gene RB [15], Rpi-blb1 [16] and Rpi-blb 2 [17] which are
active in both potato and tomato. Somatic hybrids are useful in
identifying resistance genes and in transmitting the genes into potato
breeding lines by crossing. Nevertheless, genetic modification of potato
breeding lines is presently preferred, because resistance can be
introduced into commercial lines with greater speed.
No studies done on species-specific processing of transgenic proteins to
rule out immunogenicity or toxicity
The BASF GM potato trials [18-21] involve two broad-spectrum resistance
genes, Rpi-blb1 and Rpi-blb2. These two genes code for proteins that
have a nucleotide-binding site consisting of leucine-rich repeats
(NBS-LRR) typical of a class of regulatory proteins. Many disease
resistance genes code for proteins of that class. Numerous NBS-LRR genes
are present in the typical plant genome, each protein specific for a
particular pathogen, signalling a defence response that frequently
involves a localized cell death (hypersensitive response) [22-24]. The
blight fungus suppresses the potato defence genes in sensitive plants,
but is thwarted by successful defence genes in resistant plants. The
NBS-LRR resistance genes in plants are localized in the cell cytoplasm
and do not span the cell membrane but are activated by signals from
pathogens that penetrate into the cell [23, 24]. The cell dies and traps
the invading pathogens. Plant NBS-LRR proteins generally produce
antibodies when injected into mammals, but the species-specific
processing of the disease resistance proteins, which contribute to the
immune response, has yet to be investigated.
Denial of horizontal gene transfer based on a single research paper
exposed to be fundamentally flawed
The BASF proposals [18-21] indicate that the potatoes were transformed
using two plasmids, each with single copies of the two S. bulbocastanum
resistance genes Rpi-blb1 and Rpi-blb2. The two genes were each
regulated by its own endogenous promoter (including an intron as an
enhancer) and terminator. The plasmids also contained a mutant
acetohydroxy acid synthetase (ahas) gene from the tiny mustard plant
Arabidopsis that conferred resistance to the herbicides of the
imidazolines group, which is approved for use in the UK for some crops,
but does not appear to be approved for use with field potato [25]. The
ahas gene is controlled by the nopaline synthase promoter and terminator
from Agrobacterium. The transformed potatoes are herbicide tolerant,
but the herbicide is only used during selection of transformed potato
cells, and not during cultivation of the potato.
Nevertheless, the herbicide tolerant gene is present in the GM potato
and can be transferred, along with the other transgenes, by
cross-pollination, or via horizontal gene transfer to unrelated species,
especially if the GM potato is genetically unstable, as it may be, as
the GM inserts of all commercially approved lines were found to have
rearranged since characterized by the companies [26, 27] (Transgenic
Lines Proven Unstable, SiS 20 Unstable Transgenic Lines Illegal, SiS
21). All GM lines intended for the release contain one or two copies of
the plasmid inserts, but no molecular genetic details on the inserts
were provided, nor evidence of genetic stability beyond the bald
statement that [19], “The inserts have been found stable when shoots are
propagated via cuttings. Therefore the inserts are considered to be
stably integrated into the nuclear plant genome.”
BASF dismisses horizontal gene transfer [19] citing an outdated single
reference [28] that one of us has exposed to be fundamentally flawed
[29] (Horizontal Gene Transfer – The Hidden Hazards of Genetic
Engineering). Despite the misleading title of the publication [28] that
horizontal gene transfer from the transgenic potato “occurs, if at all,
at an extremely low-frequency”, the actual results showed the opposite
was the case. A high transfer frequency of 5.8 x 10-2 per recipient
bacterium was demonstrated under optimum conditions. But the authors
then proceeded to calculate an extremely low theoretical gene transfer
frequency of 2.0 x 10-17 under extrapolated “natural conditions”,
assuming that different factors acted independently. The natural
conditions, however, were largely unknown and unpredictable, and even by
the authors’ own admission, synergistic effects could not be ruled out.
There is abundant direct and indirect evidence for horizontal gene
transfer reviewed in many ISIS publications (see recent summary in
Living with the Fluid Genome [30]).
No investigations on immunogenicity or toxicity
The expression of the modifying genes was not studied under extreme
conditions of stress such as drought, water logging, heat, cold,
nitrogen excess or starvation in glasshouse experiments. As in the past,
GM crops have been tested under optimum conditions for growth prior to
commercial or test release into the environment, where stress conditions
may lead to unexpected toxicity (as well as genetic instability) in GM
crops, of which a number of recent cases have emerged [7].
The BASF proposals [18-21] claim that the resistance genes are not
expected to exert any toxic, allergenic or harmful effects on human
health arising for genetic modification, but no feeding trials have been
carried out. The genetic modifications are assumed to be safe because
plants contain numerous NBS-LRR proteins, and cultivated potatoes
contain R genes from the wild species S. demissum. The assumptions of
safety are specious. The S. demissum genes in commercial potatoes are
NBS-LRR genes, but are not the broad-spectrum NBS-LRR genes used in the
BASF potatoes. Above all, the finding that gene transfer between related
species may nevertheless lead to proteins with powerful immune responses
[8, 9] need to be taken on board. The current procedure used to scan
amino acid sequences of proteins for epitopes (motifs) that elicit
allergic responses (involving IgE) would overlook the powerful immune
responses resulting from carbohydrate chains added during processing of
the proteins. The GM potatoes must be tested not only for allergenicity,
but also for inflammatory and other immune responses, and proven safe
before being released into the environment. Otherwise, the impacts on
humans, livestock and wildlife could be devastating.
Assumptions of safety not justified on existing evidence
BASF had petitioned for field test release of the GM potatoes beginning
2005 in the Netherlands. The notice of petition indicated that the GM
potato would be released in Germany, United Kingdom and Sweden but full
reports of the tests were not provided [31]. In the United States, there
have been five field tests with the GM potatoes in Minnesota and
Wisconsin, carried out by USDA or the University of Minnesota [32]. The
isolation and deployment of the RB genes in potato has been described
[33, 34].
Field-testing of broad-spectrum NBS-LRR genes has begun with the potato
blight resistant strains. Broad-spectrum pest-resistant strains of rice,
maize, soybean, and numerous food crops will soon follow. It is
imperative that the safety of these genetic modifications to health and
the environment be fully evaluated before the GM crops are released in
field trials. The proposition that the NBS-LRR family of plant pest
resistance genes and their products are safe for humans and for the
environmental because they are found in food crops and hence require no
further testing is simply not justified on the basis of existing evidence.
The UK government must withdraw permission for the trials, or else the
regulators should be held responsible for any harm caused.
********************************************************
To unsubscribe from SANET-MG:
1- Visit http://lists.sare.org/archives/sanet-mg.html to unsubscribe or;
2- Send a message to <listserv@sare.org> from the address subscribed to the list. Type "unsubscribe sanet-mg" in the body of the message.
Visit the SANET-MG archives at: http://lists.sare.org/archives/sanet-mg.html.
Questions? Visit http://www.sare.org/about/sanetFAQ.htm.
For more information on grants and other resources available through the SARE program, please visit http://www.sare.org.