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[SANET-MG] a pig in a poke
March 25, 2005
Buying Syngenta Genetically Modified Maize: A pig in a poke?
Buying a pig in a poke is a rural derisory term for something
bought or bargained for, without the quality or the value being known.
Farmers who purchased Syngenta genetically modified (GM) maize Bt11
may, in fact have purchased “a pig in a poke” because many were recently
found to have purchased Bt11 but received another GM variety called Bt10
according to a report first published in the science journal Nature. The
report indicated that several hundred tones of the unapproved GM maize
variety Bt10 had been “inadvertently” distributed under the Bt11 label
between the years 2001 and 2004. Syngenta claimed that Bt11 and Bt10
were physically identical (1). As will be shown in the following
discussion eleven years ago the Northrup-King company (later taken over
by Syngenta) reported that Bt10 produced several times less toxin in
mature leaves than did Bt11 even though the two lines were modified with
similar sets of transgenes which were inserted at different loci in the
maize genome. The reply of Syngenta to the distribution of unauthorized
GM maize seems to contradicted by their own reports to USDA/APHIS in 1994.
Before going into the data on Syngenta Bt10 it might be useful to have
an overview of the main commercial strain Syngenta Bt11. Bt11 has been
approved for consumption in Argentina ,Australia,Canada,China ,European
Union, Japan,Korea,Philippines,Russia, South
Africa,Switzerland,Taiwan,United Kingdom,United States and Uruguay (2).
Northrop-King Company (later taken over by Syngenta) Consulted the US
Food and Drug Agency (FDA) provided minimal evidence that the maize
strain was substantially equivalent to unmodified maize (3,4).
USDA/APHIS considered petition 95-195-01 for non regulated status of
Bt11 corn .and that agency determined that Bt 11 corn shall no longer
be a regulated article in 1996.. The Northrup-King petition for non
regulated status of Bt11 maize was submitted in 1995 and that petition
provides fundamental data on the molecular organization of Bt11 and
information on its agronomic performance(6). The information provided
below is from that document.
A plasmid vector ZO1502 was used to introduce two structural genes
into maize., a synthetic approximation of the Bacillus thuringiensis var
kurstaki HD-1 Cry1Ab toxin gene that had been altered in coding sequence
and shortened to enhance its production in maize was driven by the 35S
Cauliflower Mosaic Virus (CaMV) with an intron from maize alcohol
dehydrogenase gene as an enhancer, transcription was terminated using
NOS terminator from Agrobacterium. The other structural gene introduced
into maize was a synthetic approximation of the Phosphoinothricin acetyl
transferase (PAT) gene from Streptomyces which had been altered
extensively including the start codon and numerous codon changes to
decrease GC content and to enhance production in maize. The PAT gene
confers resistance to the herbicide glufosinate but the GM maize was not
marketed as herbicide resistance. The PAT gene was driven by the 35S
CaMV promoter , with maize alcohol dehydrogenase enhancer, while
transcription was terminated by the NOS gene from Agrobacterium. The two
structural genes were inserted into the long arm of maize chromosome 8.
The proteins produced from the synthetic structural gene were claimed
to be “identical” to the proteins produced in bacteria (the bacterial
proteins were used in safety evalustions). However the criteria used to
establish that the proteins were identical were crude and not very
convincing. The comparisons were based on gel electrophoresis and on
limited sequence analysis of proteolytic fragments of the proteins.
The comparisons were not very convincing and should have compared the
entire amino acid sequences of the proteins.
An appendix to the Northrup King petition compared the production of
the events Bt11 and Bt10. The Bt10 event was not characterized as to
the chromosomal site of integration nor was there extensive analysis of
the gene inserts and their protein products. The study showed that
Bt11 produced more toxin protein than Bt10, mature leaves contained
about seven times more toxin in Bt11 than in Bt10. These results show
that there is clearly fundamental differences between the two events.
The lower level of toxin production would mean that farmers unknowingly
planting Bt10 in place of Bt11 would be prone to experience insect
resistance in the low toxin maize. There has been some,as yet,
unsubstantiated reports that the Bt10 inserts have a promoter gene that
is different from Bt11 or the enhancer gene has been altered.
Furthermore , there has been hints that Bt 10 contains an antibiotic
resistance gene while Bt11 has none. Clearly, the toxin proteins and
gene must be fully studied and those studies must be made public as soon
The Australia-New Zealand Food Authority review of reported that the
Bt11 PAT gene is driven by the 35S Figwort Mosaic Virus (8) rather
than the 35SCaMV promoter reported to USDA/APHIS (8). Both cannot be
correct because there should be only one Bt11 insert. The Canadian Food
Inspection Agency reported that there was more than one Cry1Ab toxin
protein produced in Bt11,these included a 69kDa protein,
a 65kDa protein and two minor proteins of 40kDa and 15 kDa. The toxin
seems to be processed or degraded in event Bt11 maize. The behavior of
the toxins produced in event Bt10 have not been fully reported to public
and this information should be made available forthwith.
There was a long delay between the finding of large plantings of Bt10
and the report of these findings to the public. Heretofore, both
Syngenta and FDA have claimed that Bt10 and Bt11 are identical. This
claim was made in the face of clear evidence that the two events were
different. Presently, the corporation and their regulator seem to have
conspired to commit fraud on the public. The regulators should not delay
making a full exposure of all of the data, otherwise they will create a
growing distrust of the regulatory system.
1.Macilwain,C. US launches probe into sales of unapproved transgenic
corn Nature 2005,434,424
2. Agbios Bt11 approvals http://www.agbios.com/
3.US Food and Drug Administration Biotechnology Consultation Agency
Response Letter BNF No.000017 1996 http://www.cfscan.fda.gov/
4. US Food and Drug Administration Biotechnology Consultation Note on
the File BNF No.000017 1996 http://www.cfscan.fda.gov/
5.Payne,J. USDA/APHIS Petition 95-195-01 for Determination of
Nonregulated Status for Bt11 Corn 1996
6.Pilacinski,W. and Williams,D. Petition for Determination of
Nonreguloated Status for: Insect protection corn expressing the Cry1Ab
gene from Bacillus thuringiensis var. kurstaki 1995
7.Hanten,J. and Meeusen,R. Petition for Determination of Nonreguloated
Status for: Insect protection corn expressing the Cry1Ab gene from
Bacillus thuringiensis var. kurstaki Appendix G Determination of levels
of plant produced Bacillus thuringiensis kuastaki HD-1 proteins in
transgenic maize. 1994
8.Australia-NewZealand Food Authority Draft Risk Analysis Report
Application A386 Food derived from insect protected herbicide tolerant
Bt11 corn 2000
9.Canadian Food Inspection Agency Decission Document DD96-12:
determination of environment safety of Northrup King Seeds European
corn borer resistant corn 1996
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