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[SANET-MG] beware vistive soy



ISIS Press Release 25/11/04
Beware Monsanto’s "Vistive Soybeans"
Prof. Joe Cummins lifts the lid on a new wave of genetically engineered
products that claim to offer "healthier foods" and "direct consumer
benefits".

A fully referenced version of this article is posted on ISIS members’
website. http://www.i-sis.org.uk

In September 2004, Monsanto announced a "Vistive soybean" with reduced
linolenic (low linolenic or LL) acid content that will be available for
planting in the 2005 season. Although promoted as "produced through
conventional breeding" because it includes natural genes reducing the
oil content of linolenic acid, Vistive also has transgenes conferring
the Roundup Ready trait.

Vistive soybean does not appear to have been approved under the usual
procedure for transgenic crops because the reduced linolenic acid
content was achieved using traditional selection and breeding. Instead,
government regulators assumed that the Roundup Ready trait acts
independently of the LL trait and for that reason the two kinds of
traits could be joined by crossing two strains.

Certainly, there is no precedent for reviewing and approving novel crops
produced by conventional breeding, but if the LL trait interacts with
the Roundup Ready (glyphosate tolerance) trait, Vistive soybeans should
be re-evaluated as an alteration to the original Roundup Ready trait.
There is a clear indication that the use of glyphosate on the soybean
crop will result in an impact on fatty acid metabolism through the
breakdown products of the herbicide (see later).

Vistive soybeans with the Roundup Ready trait are claimed to contain
less than 3% linolenic oil, in contrast to the 8% linolenic content for
conventional soy oil. Low linolenic oil is more stable, with a better
flavour and requires less hydrogenation. Trans fatty acids are produced
in the hydrogenation process; and trans fatty acids are linked to heart
disease because they lower HDL (good) cholesterol while raising LDL
(bad) cholesterol. Ironically, trans-fats labelling is to begin in 2006
in the United States, even though industry and regulators in the United
States resist labelling of products containing transgenes.

In plants, fatty acids are produced in the chloroplasts. Two molecules
are crucial for fatty acid synthesis: acetyl-CoA and malonly-CoA
(acetyl-CoA with an added carbon dioxide molecule). The number of carbon
atoms in the long fatty acid chain is always even, and the carbon
molecules are added two at a time. The newly synthesized fatty acids may
be altered in mitochondria, or the endoplasmic reticulum, or stored in
membrane bound lipid vesicles.

Catabolism of the fats is undertaken in organelles called glyoxysomes
where the fatty acids are degraded two carbon atoms at a time, by a
process called beta-oxidation. Fatty acids are modified in organelles
and the endoplasmic reticulum by the lipoxygenase pathway to produce
plant defence and signalling compounds such as jasmonates. Glyoxysomes
carry out the glyoxylate cycle - a modification of the tricarboxylic
acid cycle found in plants and microbes - as well as beta-oxidation.
Fatty acid metabolism is crucial to energy transformation in plants, but
also contributes to cell structure and to signalling and defence.

The transgenic parent of Vistive soybean is the soybean line GTS40-3-2
(event MON-04032-6), tolerant to glyphosate. The strain was released
commercially in the United States in 1994, then Canada (1995), Japan
(1996), Argentina (1996), Uruguay (1997), Mexico (1998), Brazil (1998)
and South Africa (2001). The transgenic construct includes a synthetic
approximation of the EPSPS gene from Agrobacterium for tolerance to
glyphosate, adjusted for the codon preference of the crop. The EPSPS
gene was driven by the enhanced 35s cauliflower mosaic virus promoter,
and the sequence included a chloroplast transit protein from petunia and
a nopaline synthesis terminator from Agrobacterium .

Six years after Roundup Ready soy was released to the environment,
Monsanto acknowledged that an "inactive" 75 base pair fragment and a 250
base pair fragment of the EPSPS gene were inserted outside the open
reading frame of the EPSPS protein (those inserts were over 20% the size
of the EPSPS gene). The origin of the gene fragments and their possible
activity was curtly dismissed without fuller explanation. The evident
instability of these and other crop transgenes has been discussed by
Mae-Wan Ho, and raises many biosafety concerns.

Possible interactions between the LL and Roundup Ready genes of Vistive
soy cannot be dismissed, as the crop will certainly be sprayed with
glyphosate. The herbicide will accumulate to levels toxic to animals and
humans if it is not broken down in the plant cell. In plants, glyphosate
is normally broken down by glyphosate oxidase (GOX) enzyme (presumably
an enzyme present to digest natural products). GOX enzyme accelerates
the breakdown of the herbicide glyphosate into two compounds,
aminomethylphosphonic acid (AMPA) and glyoxylate. Glyoxylate is commonly
found in plant cells and is further broken down by the glyoxylic pathway
for lipid metabolism. The increased concentration of glyoxylate due to
glyphosate breakdown would certainly disturb the metabolism of fatty acids.

Glyphosate exposure of herbicide tolerant groundnut was observed to
increase glyoxylase enzyme. Presently, it is not possible to predict the
nature and extent of disturbance of fatty acid metabolism, nor the
impact on LL function. The point is that there is a clear link between
Roundup Ready and LL traits, which should be explored fully before the
Vistive crop reaches general distribution. Every transgenic crop should
be reassessed after it has been crossed with a variety derived from
conventional selection, especially one that has a clear metabolic
association with the transgene, before any release of the crop. There
should be a rule to ensure that careful reassessment is done.

The burden of proving that releases such as Vistive are safe rests with
the proponent. Experiments must be done to ensure that the Roundup Ready
genes and the LL genes are independent of each other, and that any
interactions are fully risk assessed. In addition, Roundup Ready soybean
itself should be reassessed in light of new scientific evidence raising
questions about transgenic instability.

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