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Re: Syngenta
Hi Evon Kochey,
Below is something I drafted on VIP3A. The main concern , to me, was
that the VIP toxin protein being tested for mammalian and environmental
safety was the toxin produced in bacteria. The actual toxin in the
crop plant is a synthetic modification of the bacterial gene ahd it has
altered gene and protein sequences. In the VIP toxins the death
sequences are related to death sequences in mammals, such sequences have
both good ( for example virus killing by cell suicide) or bad (say
destruction of tissue cells).Sincerely,Joe
November 3, 2003
Prof. Joe Cummins
e-mail: jcummins@uwo.ca <mailto:jcummins@uwo.ca>
“VIP3A is a new Bt toxin looming over out food”
The bacterium, Bacillus thuringiensis (Bt), has proven to be a
rich source of toxins for killing insect pests. Most of the toxin genes
now being used in genetic engineering are produced in sporulating Bt,
these genes are designated Cry 1, Cry 2 etc. up to at least Cry 41.
The Cry genes are further designated Cry 1 A, Cry 1 B etc. for
sequence variations in the gene and protein toxin, then further
refined to Cry 1 Aa etc. for very small differences in sequence(1).
The Cry gene toxins target specific insect cell receptor proteins and
create pores that lead to osmotic lysis of the insect gut cells. Only a
few Cry genes have found favor in genetically modified (GM) crops.
Along with the Cry genes Cyt genes have been characterized that are
genetically distinct from Cry genes and act by hemolysis of the insect
blood cells(2). In recent years vegetative insecticidal proteins (VIP)
have been found to have potent broad spectrum activity against insects
(3). VIP genes are not homologous to Cry and Cyt genes and bind to cell
membrane proteins different from the other toxins (4,5).
Syngenta corporation, producers of chemical and biological
pesticides, has patented the VIP genes for use in transgenic crop
plants and microbes (6). Syngenta United states patent 6,429,360 covers
the use of Bt VIP genes and their synthesis and alteration to improve
performance in crop plants. The Syngenta patent provided evidence
that VIP3 A toxin produced apoptotic type of cell death, including a
series of cytological changes including production of membrane bound
apoptotic bodies and activate endonuclease enzymes that cleave
chromatin into discrete fragments. Apoptosis (meaning petals falling
from a flower) is a form of programmed cell death common to all cells
with discrete nuclei. Apoptosis is a part of normal development of
organisms but the VIP3A toxin uses programmed cell death to destroy the
cells of the insect gut. In order to function fully in the plant cells
the Bt VIP3A gene is modified in its coding sequence and by the
addition of a strong promoter, an intron to facilitate transfer of the
pre-messenger RNA from nucleus to cytoplasm and transcription
terminator and polyA addition sequences. The insect VIP3A receptor was
identified and its characteristic “death” recognition sequence was
characterized. Organisms whose cells have nuclei generally have
receptors with death signals and the insect VIP3A receptor is a unique
member of the class of sequences.
Syngenta has petitioned the United States Environmental
protection Agency (EPA) for commercial release of event COT102 cotton
containing a synthetic VIPA3 gene (7). Presumably corn containing the
VIP3A gene will be proposed for commercial release. The EPA report of
the Syngenta petition for tolerance in or near food (7) reported that
the VIPA3 toxin was homologous to the VIP3A toxin in numerous Bt strains
. However, the petition failed to mention the numerous change in DNA
sequence including promoter, introns , terminator and polyA signal. Many
changes in the code for the VIPA3 toxin were reported in the Syngenta
patent for VIP genes. Mammalian acute toxicity studies were done
using the VIPA3 toxin produced in bacteria not the toxin produced in
modified corn or cotton. The VIPA3 toxin in cotton is assumed to be
substantially equivalent to the toxin produced in bacteria but , as in
the case of most other commercial Bt cry toxins, the toxin protein is
allowed to diverge significantly from the bacterial toxin so long as the
protein remains active against insect cells and is immunologically
similar to the toxin produced in cotton.. The toxin tested by Syngenta
showed no overt acute toxicity and there was no indication that it was
allergenic. Sequence analysis showed no overt similarity to known toxins
The practice of putting forward Bt toxins produced in bacteria as
equivalent to the Bt toxins produced in crops was discussed earlier (8).
The practice is unsound and should, at least, be made very clear in the
government announcements on the safety testing of GM crops bearing genes
for Bt toxins.
The EPA report notes ”Once in the insect gut, the VIPA3
protein binds to specific receptors (different from those by Cry 1A
proteins) and forms ion specific pores.” There was no discussion, in the
EPA report (7) of the apoptosis and binding to death sequences receptors
mentioned in the Syngenta patent (6). Indeed, the claim that the VIP3A
toxin had no obvious homology to mammalian toxins seems to have ignored
the relative homology of apoptosis receptor death sequences. The
difference in fundamental processes between the Syngenta patent (6) and
the EPA report (7) is perplexing because the patent document was well
supported with experiments while the EPA report provided little
scientific evidence for its claims.
In conclusion, the Bt toxins of the VIP gene family provide
potent broad spectrum insect control. The toxins have been reported to
act by binding to death sequences and triggering apoptosis in insect
cells. The potential impact of such toxins on the receptors and death
sequences in mammalian cells should be fully evaluated before GM crops
bearing the toxins enter the mammalian food chain.
References
1. Crickmore,N. “Full list of delta endotoxins” 2003
http://epunix.biols.susx.ac.uk/home/Neil_Crickmore/Bt/toxins2.html
2. Guerchikof,A,DeleCluse, A,and Rubinstein, C. “The Bacillus
thuringiensis cyt genes for hemolytic endotoxins” 2001 Appl. and Envir.
Microbiology 67,1090-6
3. Estruch,J,Warren,G, Mullins,M, Nye,G,Craig,J and Kozeil,M “Vip3A,
a novel Bacillus thuringiensis vegetative insecticidal protein with a
wide spectrum of activities against lapadopteran insects”1996 Proc.
Natnl. Acad.Sci USA 93,5389-94
4. Yu,C,Mullins,M,Warren,G, Kozeil,M. and Estruch,J. “The Bacillus
thuringiensis vegetative insecticidal protein vip3A lyses midgut
epithelium cells of susceptibale insects” 1997 Appl. and Envir.
Microbiology 63,532-6
5. Lee,M.,Walters,F,Hart,H,Palekar,N and Chen,J. “The mode of action
of the Bacillus thuringiensis vegetative insecticidal protein Vip3A
differs from that of Cry 1Ab” 2003 Appl. and Envir. Microbiology 69,
4648-57
6. Estruch,J,Warren,G,Desai,N,Kozeil,M, and Nye,G. “ Plant Pest
Control” 2001 US Patent 6,429,360 pp 1-25
7. US Environmental protection Agency “Bacillus thuringiensis VIP3A
insect control protein; Notice of filing a pesticide petition to
establish a tolerance for a certain pesticide chemical in or on food”
2003 Federal Register 68,number 109,33942-6
8. Cummins,J. “More on Bt Resistance” 2003 http://www.i-sis.org.uk/
Evon Kochey wrote:
http://www.epa.gov/fedrgstr/EPA-PEST/2003/November/Day-26/p29185.htm
Description: Bacillus Thuringiensis VIP3A Insect Control Protein
as Expressed in Event COT102; Notice of Filing a Pesticide Petition to
Establish an Exemption from the ...
Syngenta is petitioner
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