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  • From: "Tradingpost" <tradingpost@gilanet.com>
  • To: livingontheland@lists.ibiblio.org
  • Subject: [Livingontheland] Rice War Continues
  • Date: Tue, 30 Nov 2004 10:12:27 -0700

The Institute of Science in Society Science Society
Sustainability http://www.i-sis.org.uk

General Enquiries sam@i-sis.org.uk Website/Mailing List
press-release@i-sis.org.uk ISIS Director m.w.ho@i-sis.org.uk
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Rice War Continues

Editor’s note

The productivity of rice has been falling along with that of
other food grains. Chief among the causes of the fall in
productivity are severe water shortages due to over-
irrigation and depletion of aquifers, eroded soils from
over-application of chemical fertilizers and pesticides, and
rising temperatures from global warming.

While innovative farmers have been addressing these problems
with a range of effective measures to increase yields
through regenerating degraded soils, conserving water and
minimizing inputs (see many articles in SiS23), pro-GM
scientists in the three major rice-growing countries, China,
India and Japan, have all been researching and promoting GM
rice with scant regard for safety or sustainability.

We are circulating Professor Joe Cummins’ review on GM rice
in China http://www.i-sis.org.uk/GMRIC.php, and making
available two others, on GM rice in India and Japan
respectively on ISIS’ website:

GM Rice in Japan
http://www.i-sis.org.uk/GMRIJ.php
GM Rice in India
http://www.i-sis.org.uk/GMRII.php

ISIS Press Release 30/11/04

GM Rice Release in China?
**********************

Reduced production and transportation bottlenecks have
persuaded China to think of growing GM rice, but Prof. Joe
Cummins jcummins@uwo.ca says it is unwise for serious safety
reasons.

The references for this article are posted on ISIS members’
website. Details here.

GM rice a solution to rice shortfall?

Remote sensing data reveal that China has about 1.27 million
square miles of cropland. Annual rice production, as a
single or double crop, or cropped with wheat or oilseed
rape, accounts for about 19% of the cropland in China [1].
Rice is far and away the most important food crop in China.

At the same time, agricultural biotechnology is growing
faster in China than in any country apart from the United
States. In 2002, China announced regulations for biosafety
management of genetically modified (GM) crops and rules for
labeling GM products [2].

This year, rice prices rose about 27% in China because of
reduced production and transportation bottlenecks; and it
was thought that commercializing GM rice could solve the
problem.

The government reportedly set aside one billion dollars to
hasten the commercial release of GM rice to farmers [3].
Even though there has been extensive research on GM rice in
China, it is not yet clear which GM rice varieties will be
selected for first release to farmers. Likely candidates may
be among those featured in recent scientific publications in
international journals.

Insect resistant rice

Insect resistant rice tops the list of likely candidates for
commercial release; the most widely used transgenes being
the Cry toxins isolated from the soil bacterium Bacillus
thuringiensis (Bt). There are a number of Cry toxin
proteins, each specific for a range of insect pests.
Individual cry genes and their proteins are identified by a
number 1, 2, 3 etc., followed by a letter A, B, C etc. That
letter is followed by a lower case letter a, b, c, etc. The
numbers signify a cry gene on the bacterial chromosome,
while the letters signify the alleles (different forms) of
the gene; the upper and lower case letters indicate
respectively greater and lesser DNA code letters differences
between the alleles, which in turn determine their
toxicities to different insect pests.

A gene fusion protein toxin made up of two different
synthetic Cry toxins - Cry1Ab fused with Cry1Ac - has been
inserted into Indica rice [4]. The fusion protein was under
the control of the rice actin promoter with its first intron
and the nos gene terminator, tnos, from the soil bacterium,
Agrobacterium. The fusion toxin was active against two
insect pests of rice, leaf folder and yellow stem borer.
However, the fusion toxin does not appear to have been
tested for mammalian toxicity and it has not yet been used
in any GM crop that has been released commercially.

About a third of rice lines transformed with Bt toxin Cry1Ab
or Cry1Ac suffer genetic aberrations, such as chlorophyll
deficiency or stunted plants. The variability was ascribed
to ‘somaclonal’ variation [5], the consequence of genetic
instability common to the plant tissue culture technique
used in creating the GE lines. It is thought to result from
the activation of mobile genetic elements or transposons
that frequently insert into and disrupt the rice genes. Such
insertion mutations are capable of creating unexpected
toxins and for that reason cannot be ignored.

Research has shown that rice leafhoppers are controlled by
GM rice with Cry1Ab toxin. The synthetic cry1Ab gene was
placed under the control of the maize ubiquitin promoter,
linked in tandem with gus (encoding the b-glucuronidase, a
positive selection marker), and the negative selection
antibiotic resistance markers hpt (encoding hygromycin
resistance), and npt (encoding neomycin resistance) [6]. The
GM rice reduced leafhopper damage, but there has not been
much study on the environmental and human-health impacts.

Straw from GM rice containing Cry1Ab was found to alter
important biological properties in water-soaked soil,
indicating a shift in the metabolic activities of the soil
[7]. In China, rice straw is usually incorporated along with
the plant residues into soil to enhance fertility, so the
implications of these changes are important.

There are both scientific and anecdotal evidence, reviewed
in earlier reports, suggesting that the natural Cry toxins
pose serious health hazards to human beings and animals. Bt
spores containing a mixture of different Cry toxins caused
allergic reactions in farm workers [8]. Cry1Ac, in
particular, has been shown to be a potent immunogen [9, 10].
The synthetic Cry toxins incorporated into GE crops differ
from the natural toxins in many respects and are often
hybrids of two or more Cry proteins. These synthetic
proteins are completely unknown and untested for their
toxicities and allergenicities [11].

A screening of transgenic proteins expressed in market-
approved transgenic food crops against known allergens in
the public databases raised further concerns [12]. Twenty-
two out of 33 proteins screened were found to have stretches
of identities with known allergens, and therefore "warrant
further clinical testing for potential allergenicity". These
include all the Cry toxins, the CP4-EPSPS and GOX
(responsible for glyphosate tolerance), many viral coat
proteins (viral resistance) and even proteins encoded by
marker genes such as GUS.

The Galanthus nivalis (snowdrop) plant lectin gene (gna) was
used to protect rice from the small brown planthopper [13].
The genetically engineered rice contained the gna gene,
driven by the phloem-specific Rss1 promoter, accompanied by
the markers hpt gusA, both driven by the cauliflower mosaic
virus (CaMV) 35S promoter. While the GM rice controlled the
sap-sucking insect [8], further studies on the safety of GNA
rice should be undertaken because GNA potatoes containing
the snowdrop lectin and the CaMV 35S promoter were found to
increase proliferation of the gastric mucosa, and the
hyperplasia was attributed to the transgenic construct or
process [14].

Disease resistant rice

One of the most devastating diseases of rice in Africa and
Asia is bacterial leaf blight (BB), which is caused by the
Gram-negative bacterium Xanthomonas oryzae pv. oryzae (Xoo).
The rice gene Xa21 provides resistance against some races of
Xoo, although the endogenous gene is expressed at a low
level.

A ferredoxin-like protein from sweet pepper was found to
confer resistance to Xoo. Ferredoxins are iron-sulphur
proteins that mediate electron transfer in a range of
metabolic reactions, and plant type ferredoxin is located in
the chloroplast membrane.

The sweet pepper ferrodoxin gene (ap1) was inserted in the
rice genome to confer resistance against BB [15]. Ap1with
the chloroplast transit peptide was driven by the CaMV
promoter and transcription terminated by tnos. The
transgenic rice also contained the marker genes gusA and
hpt, both driven by the CaMV 35S promoter and terminated by
tnos.

Enhanced resistance to BB was conferred using the rice Xa21
gene. However, the transformation included the bacterial
hygromycin antibiotic resistance marker and the gus marker
along with the bacterial beta-galactosidase (z) gene [16],
not to mention the CaMV 35S promoter and Agrobacterium nos
terminator. Transferring genes from rice to rice using
genetic engineering, rather than crossing and selection, was
justified by the researchers, as they considered the
conventional crosses needed to separate Xa21 from flanking
genes that were undesirable too time-consuming. Yet,
molecular marker-assisted selection has actually been used
to introduce the Xa21 gene into rice cultivars using
conventional breeding and selection [17]. The marker-
assisted variant of conventional breeding and selection
provides the advantage of conferring BB resistance, while
avoiding the insertion of antibiotic markers and other
potentially problematic genes into rice.

Rice blast is one of the most important diseases of rice
worldwide; and is caused by a fungus, Pyricularia oryzae
(Pyricularia grisea), which can attack the aerial parts of
the rice plant at any stage of growth. Trichosanthin, a
protein isolated from the medicinal Chinese cucumber,
Trichosanthes kirilowii, was found to control the rice blast
fungus. The gene for trichosanthin was introduced into rice,
driven by the CaMV promoter and terminated by tnos. Rice
with the trichosanthin gene resisted the blast disease [18].
However, trichosanthin has long been used to produce
abortion in humans and is immunosuppressive and can induce
renal toxicity [19]. The immunosuppressive ability of
trichosanthin has been used to treat HIV/AIDS and cancer. It
is clear that exposure of the general public to GM
trichosanthin rice is unwise.

A conventionally-selected rice resistant to blast disease
has been pyramided (pyramiding is conventional crossing and
selection) with transgenic rice carrying the Xa23 gene, to
induce tolerance to both the fungal and the bacterial
diseases [20]. Xa23 comes from rice, but it has regulatory
genes from other organisms associated with it, so it is a
transgene. The full health and environmental implications of
pyramiding genes have yet to be considered. At the very
least, the toxicity of each transgenic toxin, and the
combinations of toxins brought about by crossing must be
considered and assessed for risks.

Safety concerns still to be addressed

Scientific research on transgenic crops in China has focused
on the control of important pests and diseases. However, the
remedies appear to have had little scrutiny regarding human
health and environmental (including the implications of gene
flow to wild and weedy relatives of rice) impacts.

In the case of Bt rice straw on wet soil there is evidence
of a clear impact that bears fuller study. Concerns about
the impacts of insect resistant rice on non-target organisms
and of the development of insect resistance have been raised
for other Bt crops, and these must be considered in relation
to GM rice as well.

The Bt cry genes used in insect resistant rice are synthetic
approximations of the real bacterial gene, altered for high-
level production in rice plants. It is thus crucial that the
real toxin from Bt rice, not the bacterial surrogate, is
tested for health and environmental impacts.

The use of antibiotic resistance marker genes in GM crops is
an acknowledged risk factor, with European legislation
mandating a phasing out of such marker genes. This is
because of the serious concern of potential gene transfer to
pathogenic bacteria, which could compromise the treatment of
diseases. Most of the GM rice lines reviewed here have used
antibiotic resistance marker genes, and this factor must be
adequately considered in the risk assessment.

In addition, the potential of the CaMV 35S promoter to cause
genetic instability, genome rearrangements, and secondary
gene transfer into genomes of animals including humans [21],
should also be given sufficient consideration.


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This article can be found on the I-SIS website at
http://www.i-sis.org.uk/GMRIC.php





  • [Livingontheland] Rice War Continues, Tradingpost, 11/30/2004

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