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[SANET-MG] putrid rice?
It has been sugested that the crop should be called putrid rice?
http://www.i-sis.org.uk/DRGMrice.phpISIS Press Release 24/09/04
Drought Resistant GM Rice Toxic?
Prof. Joe Cummins explains why one method to genetically engineer
drought resistant rice could be perilous for human and animal health
References for this article are posted on ISIS members' website. Details
Commercial genetic engineering has been based on inserting a single
transgene along with control elements into a crop plant. Traits such as
herbicide tolerance, insect resistance and virus resistance have been
commercialized without much understanding of the metabolic consequences
of the alterations.
To deal with more complex and agriculturally significant traits, a
technique called metabolic engineering has been developed  to retune
endogenous metabolic pathways.
Recently, transgenic rice modulated in the polyamine biosynthetic
pathway has been found to be drought tolerant [2, 3]. Polyamines are
carbon chains containing two or more amine (NH 2 ) groups. Polyamines
are essential compounds found in all living cells. They increase as
bacteria putrefy animal flesh, producing a strong rotting odor.
Polyamines are given names such as putrescine and cadaverine or spermine
and spermidine. Even though the polyamines are essential for cell
growth, they may also cause disease in animals.
In animals and fungi, putrescine is the precursor of spermidine and
spermine ; it is synthesized from the amino acid ornithine. Plants have
an alternative pathway that converts the amino acid arginine to
putrescine, using the enzyme arginine decarboxylase (ADC) , the product
of the adc gene. This is followed by additional reactions to form
spermidine and spermine using S-adenosylmethionine and the action of the
enzyme S-adenosylmethionine carboxylase (SAMDC), the product of the
Rice plants were transformed with the ADC gene from Datura (Jimson weed,
a traditional and commercial source of drugs), driven by the maize
ubiquitin promoter and the first intron; and transcription was
terminated with the Agrobacterium nos transcription terminator. The
transgenic rice plants had elevated basal levels of putrescine, that
were further elevated during drought stress, leading to enhanced
production of spermidine and spermine by increased SAMDC enzyme.
The exact mechanism by which increased putrescine increases drought
resistance is not fully understood but it is clear that elevated
putrescine levels activate spermidine and spermine synthesis that, in
turn, regulate putrescine production and sets in motion the resistance
to stress [2, 3]. The transgenic rice is designed to provide sustainable
rice production under stress conditions.
Stress resistant rice has been reported without reference to the
potential impact of the metabolic alteration – such as increase in
polyamines - on mammals consuming the transgenic rice. Polyamines are
known to be elevated in the cells and body fluids of cancer patients.
Drugs inhibiting the synthesis of polyamines can prevent cancer and have
been used in cancer treatment .
Moreover, polyamines can give rise to toxic products. Spermidine and
spermine can be metabolized to hydrogen peroxide, ammonium and acrolein,
which are toxic to cells . Polyamines can contribute to the suppression
of immunologic reactions in the lung . Polyamines are implicated as
uremic toxins leading to renal failure . Chicken feed containing
elevated amines, such as putrescine, performed poorly and caused a
condition called “necrotic cellular debris” . Wines may contain
elevated polyamines from grape must and fermentation. It is believed
that spermidine and spermine may be beneficial in wine while putrescine
and cadaverine are linked to symptoms such as nausea, sweating and
difficult breathing .
The good-news message that transgenic rice may be grown under drought
conditions should be tempered by the bad-news that eating the transgenic
rice may make one quite ill. The promotion of this transgenic crop along
with others in the scientific journals seems invariably to neglect the
potential adverse effects of the crop on humans and wild life. Open
field trials should not be undertaken in the absence of proper risk
assessment and toxicity tests.
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