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[SANET-MG] gmi rice in japan



http://www.i-sis.org.uk/GMRIJ.phpRice 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,
and making available two others, on GM rice in India and Japan
respectively on ISIS’ website:

GM Rice in Japan
GM Rice in India

ISIS Press Release 30/11/04
GM Rice in Japan
Prof. Joe Cummins reviews genetically modified rice in Japan and points
to overlooked dangers

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

Rice consumption in Japan
Japanese rice-consumption is eighth among nations, or about 7% that of
China. Between 1970 and 2001, per capita consumption of rice decreased
about 30% in Japan while consumption increased about 10% in China [1].
Japan is a leading nation in rice research, rivaling China, but with a
somewhat different emphasis. Japan has had a very active research
program developing genetically modified (GM) rice. Field trials of GM
rice have been reported from 1993 to 2002, and those were engineered for
rice stripe virus resistance, low allergen rice, low protein for
saki-brewing, low gluterin (storage protein), human lactoferrin,
herbicide tolerance and rice blast resistance. The largest numbers of
tests were for Monsanto Japan’s GM rice tolerant to herbicide and for
rice resistant to blast disease [2]. In 2003, Japan’s approvals for
import and planting included GM rice for virus resistance, low
allergenicity, low protein, low gluterin and herbicide tolerance [3].

Rice with human cytochrome p450 genes
There is a large volume of work on using human cytochrome p450 genes to
produce tolerance to a range of herbicides. The cytochrome p450 enzymes
are present in all organisms from bacteria to humans. There are a number
of cytochrome p450 genes and alleles for a family of enzymes involved in
detoxifying xenobiotic (artificial and hence unnatural) chemicals and in
steroid metabolism. These enzymes are believed to have originated to
prevent over-accumulation of fat-soluble chemicals in cell membranes.
The cytochrome p450 enzymes in humans break down pharmaceutical drugs
and also activate cancer-causing chemicals such as poly aromatic
hydrocarbons (PAH) and aflatoxin. Interestingly, there does not seem to
have been any attempt to adjust the codons of the human transgenes for
those preferred by plants, so perhaps the relatively low level
production of the enzymes proved satisfactory for the purpose.

GM rice plants expressing human cytochrome genes cyp2c9 and cyp2c19 were
tolerant to a range of herbicides including the sulphonylurea
herbicides; they were obtained by transformation with three separate
plasmids simultaneously. The first plasmid contained the cyp2c9 gene
driven by a CaMV promoter with seven enhancers, followed by an
un-translated sequence from alfalfa mosaic virus and the Agrobacterium
nos gene terminator tnos; accompanied by two genes for resistance to the
antibiotics hygromycin and neomycin respectively. The second plasmid
contained the cyp2c19 gene with the same regulatory sequences and
markers as the first. The third plasmid contained the gus gene
accompanied by the same regulatory genes and markers as the other two
[4]. The CYP2C9 and CYP2C19 enzymes activate the PAH carcinogen
Benzo(a)pyrene, a common air pollutant [5].

GM rice plants expressing the human cyp2b6 gene, obtained by
transformation with a plasmid containing the gene with the same
regulatory sequences and marker genes as described above, were tolerant
to the herbicide ethofumesate, to which GM rice with other cyp genes
were susceptible [6]. The CYP2B6 enzyme activates the water disinfection
chemical bromodichloromethane to produce a carcinogen [7].

GM rice plants expressing human cyp1a1, with the same regulatory
sequences and marker genes, were tolerant to a range of herbicides.
Radioactively labelled herbicides - atrazine, chlortoluron and
norflurazon - were used to study the breakdown products in the
transgenic rice. These products, many of which are potential mutagens or
carcinogens, were excreted into the soil, where they would persist in
surface and groundwater [8]. The cyp1a1 gene product has been shown to
activate many environmental carcinogens [5,9].

Rice with novel insect resistance genes
Along with the numerous commercial Bt rice strains field-tested, novel
insect control genes have been used. For example, a trypsin-inhibitor
was introduced into rice to interfere with the digestion of stem borer
insects [10]. A synthetic trypsin-inhibitor gene derived from the winged
bean with a reduced GC (guanine-cytosine) content to improve messenger
RNA production in rice was placed under the enhanced CaMV promoter (see
above) further boosted with a tobacco mosaic virus omega sequence and
the first intron of a phaseolin gene, and terminated with tnos. In
addition, a hygromycin resistance marker was also inserted.

GM rice bearing an insect pox virus gene was used to control army worm
larvae. The pox virus gene product consumed by the army worm larvae made
them susceptible to the common soil baculovirus, which are otherwise not
virulent in the larvae. The synthetic insect pox gene had an altered DNA
sequence driven by a CaMV promoter, further boosted by a non-coding
region of the rice stripe virus RNA and transcription was terminated by
tnos. A hygromycin resistance marker was also inserted. The army worm
larvae were reported to be controlled by the baculovirus after feeding
on the transgenic rice [11].

Rice to control bacterial blight
Cecropia moths have potent anti-bacterial peptides in the haemolymph
(insect blood) of their larvae. Rice bacterial blight has been very
difficult to control globally and novel antibacterial products are being
sought. The larvae of the silk moth, Bombyx mori, provided a potent
antibacterial peptide called cecropinB. The gene for that peptide was
engineered into GM rice driven by another complicated version of the
CaMV 35S promoter with enhancer 5p, the omega sequence from tobacco
mosaic virus followed its promoter and the first intron of a phaseolin
gene; a rice chitinase signal peptide was added to the cecropin
sequence, terminated by tnos. A kanamycin-resistance marker was also
introduced. The transgenic rice was reported to provide effective
resistance to bacterial infection [12].

Rice with altered growth or metabolism
Rice has been modified to enhance metabolism. The most ambitious effort
is to try to make photosynthesis more efficient. Plants are divided into
two types - C3 and C4 plants - C3 photosynthesis being less efficient
than C4. Most plants are C3, including sugar beet, rice and potatoes;
while maize and sugarcane are C4 plants. Engineering rice to become a C4
plant may therefore increase the yield of rice crops.

The enzyme phosphoenolpyruvate carboxylase (PEPC) fixes carbon dioxide
in C4 plants, while C3 plants fix carbon dioxide exclusively through an
enzyme called Rubisco. PEPC acts as a pump to raise carbon dioxide
concentration at the site of Rubisco in the chloroplast. In one effort
to enhance expression of PEPC, the transgene for that enzyme was
obtained from maize (a C4 plant) and accompanied by the maize PEPC
promoter and all of the PEPC introns and exons. A hygromycin resistance
marker was also inserted. The over-expression of PEPC failed to improve
photosynthesis [13]. The gene for another enzyme phosphoenol pyruvate
carboxylase (PCK) from a C4 weed, Urochloa panicoides (liver weed) was
also used [14] in the attempt to create a C4 rice. But there is no
guarantee that rice yields will be improved in the field even if a C4
rice is eventually created.

Dwarf rice is desirable because they resist lodging in wind and rain.
The plant hormone gibberellin controls plant height, and reducing
hormone levels will reduce plant height. Dwarf rice was created by
incorporating the gene for an enzyme that degrades the hormone placed
under the control of a strong rice promoter. Unfortunately the dwarf
rice plants failed to set seed because the hormone also participates in
seed set.

Dwarf rice that set seed and produced a good crop was produced using a
tissue specific promoter for gibberellin synthesis. The rice was
transformed with the hormone-degrading gene under control of the tissue
specific promoter and terminated with tnos, together with a hygromycin
resistance marker [15]. The semi dwarf transgenic rice has not yet been
fully evaluated for field performance.

In Japan, 30% of the agricultural land is unsuitable for rice production
because it is too alkaline. Rice suffers iron deficiency in alkaline
soil. Iron uptake can be achieved in alkaline soil by the release of
molecules called phytosiderophores from the roots of plants tolerant to
alkaline soil. Barley secretes phytosiderophores through the action of
an enzyme nicotianamine aminotransferase (NAAT). GM rice with the barley
gene for NAAT showed enhanced tolerance to low iron availability and had
a greater grain yield than conventional rice grown on alkaline soil. The
barley NAAT transgene was driven by a CaMV promoter and terminated by
tnos, and accompanied by hygromycin-resistance and neomycin-resistance
marker genes [16].

Overlooked hazards
Japanese experiments in GM rice are technically sophisticated but the
human and environmental safety of the GM crops has not yet been full
evaluated. In particular, the human cytochrome p450 genes are already
known to activate carcinogens. They should not be used in rice, which is
an important food crop that is eaten widely as a staple in Japan and
many parts of Asia. The extensive use of aggressive CaMV–based
superpromoters untested for safety, and the incorporation of human genes
will both increase the potential of transgenic DNA to invade human
genomes through illegitimate and homologous recombination, with
dangerous consequences including the creation/activation of new viruses
or cancer [17].



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