Beware Monsanto's Vistive Soybeans

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25 Nov 2004 15:22:35 -0000

 

Beware Monsanto's " Vistive Soybeans "

 

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ISIS Press Release 25/11/04

 

Beware Monsanto's " Vistive Soybeans "

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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/full/BMVSFull.php.

Details here http://www.i-sis.org.uk/membership.php.

 

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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