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[SANET-MG] gmi rice in indai



http://www.i-sis.org.uk/GMRII.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 India
Prof. Joe Cummins reviews recent genetically modified rice research in
India.

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

India is the second largest consumer of rice on the globe after China,
and more than twice that of the next country, Indonesia [1]. India
produced 93 million tonnes of rice in 2001 and 2002, and the government
is targeting 129 million tonnes by 2011 and 2012 [2]. India approved
genetically modified (GM) cotton for food, feed and fiber in 2002 and
other approvals may soon follow [3]. A lot of technically sophisticated
research on GM rice is being done in India, and I shall describe some of
it here. Currently, no GM rice variety has been commercially released in
India.

An extensive review exists on the production of transgenic rice up to
the year 2000 [4]; I shall therefore concentrate on some important
studies published since.

Insect resistant rice
Elite Indica transgenic rice containing a synthetic gene from Bacillus
thuringiensis (Bt) expressing Cry1Ac toxin had enhanced resistance to
stem borer. The cry gene was driven by the ubiquitin promoter from maize
and its transcription was terminated by the terminator of the nos gene
from Agrobacterium, tnos; and accompanied by an antibiotic (hygromycin)
resistance gene and the bacterial gus gene as negative and positive
selection markers respectively. The transformed rice lines had up to
0.25% of their total protein as Cry1Ac toxin. The successful lines
caused 100% mortality when consumed by yellow stem borer larvae [5].
Production of toxin at high levels (approaching 1% of the cellular
protein) is considered important in preventing resistance in the target
insect, but that will mean a lot of toxin consumed by humans eating the
rice. Cry1Ac is known to be a strong immunogen [6], and has also been
found to be sufficiently similar to known allergens to cause concern [7].

Stacked and pyramided insect, fungi and bacterial resistant rice
Following development of rice with single transgenic traits, it is
inevitable that transgenic varieties with multiple traits would appear,
produced by gene stacking or multiple transformations of a transgenic
line, or by crossing transgenic lines to combine their transgenes. It
appears from current research that varieties with multiple transgenes
will soon exceed varieties with single transgenic traits.

A stacked combination of Bt toxins Cry1Ab and Cry1Ac along with
tolerance to the herbicide glufosinate (bar gene) was created in order
to serve as a parental line for generating hybrid rice varieties. The
bar gene was driven by the CaMV promoter and terminated by tnos. Both
cry genes were synthetic and driven by the maize ubiquitin promoter and
terminated with tnos. The two cry gene cassettes, each accompanied by
the bar cassette, were transformed from different plasmids and ended up
at different sites in the rice genome. The resultant transgenic line was
resistant to stem borer insects and to the herbicide glufosinate [6]. An
Indica rice variety was stacked with cry1Ab and cry1Ac, plus the
snowdrop lectin gene gna conferring multiple resistance to insects and
all of these were joined to the bar gene for glufosinate tolerance with
the CaMV promoter and tnos terminator. The cry genes were driven by the
maize ubiquitin promoter and terminated with tnos while the gna gene was
driven by phloem-specific rice-sucrose synthase promoter and terminated
by tnos. The cry genes and the gna gene were inserted at different sites
in the rice genome [7]. The stacked rice variety was assumed to confer
strong insect-killing power and to guard against appearance of insect
resistance.

An elite Indica rice was modified for resistance to insects, fungal
disease and bacterial disease. One parental strain contained the xa21
gene conferring resistance to bacterial blight. The gene was isolated
from wild rice and used to transform rice, accompanied by its original
promoter and terminator. Another parental strain had a rice chitinase
gene for protection against the sheath blight fungus and a synthetic cry
gene consisting of the fused active portions of cry1Ab and cry1Ac to
protect against yellow stem borer. The fused cry gene and the chitinase
gene were integrated at the same site on the rice genome. The cry fusion
gene was driven by the maize ubiquitin promoter and the chitinase gene
was driven by the CaMV promoter. The two parental lines were combined by
crossing to create the pyramided strain resistant to three kinds of
pathogens, insect, fungus and bacteria [8].

Another technique, marker assisted selection, has been combined with
pyramiding and stacking to produce rice resistant to fungal blast and
bacterial blight. Marker assisted selection is traditional breeding
assisted by molecular markers in the rice genome which are used to
follow desirable genes in a cross. Two rice genes for blast resistance
were identified and pyramided, and both of the pyramided lines were
stacked by modification with the rice xa21 gene accompanied by a
bacterial hygromycin resistance gene driven by a CaMV promoter. The rice
pyramid was resistant to both blast and blight [9]. Pyramiding, stacking
and fusing genes are being used with a vengeance against pests, with
little consideration for the safety of the rice, which would be consumed
as food.

Novel genetic approaches
The plant’s natural defense against pests includes an oxidative burst
mediated by hydrogen peroxide. Such a burst may mean suicide for the
plant cell and a few neighboring cells; but it saves the plant from the
invading pest. A fungal glucose oxidase (gox) gene was used to release
hydrogen peroxide in the transformed rice, driven by a rice wound
inducible promoter. The transformation also included a bacterial
hygromycin resistance gene as a selectable marker. A transformant was
resistant to both bacterial and fungal pests; and the resulting rice
strain had broad-spectrum disease resistance [10].

Flavonoid pigments such as a purple anthocyanin pigment from maize have
been found to increase blast resistance. A maize gene for an enzyme
triggering purple pigment production was used to transform rice, under
the control of a rice actin promoter and accompanied by a bacterial
hygromycin resistance gene driven by a CaMV promoter [11]. The purple
rice resisted rice blast.

Drought limits crop yields. A barley gene hva1 protects the cell
membrane during drought, and when inserted in rice, could reduce drought
damage. The rice was transformed with the barley hva1 gene, driven by
the rice actin promoter and terminated with a potato protease
terminator. The rice transformation also included the bar gene for
herbicide tolerance as a selectable marker driven by a CaMV promoter and
terminated with tnos. The transgenic crop showed greater growth than the
non-transgenic line under drought conditions [12].

Heat tolerance is important in most rice producing countries. It has
been found that a heat shock protein (hsp 100) is produced during heat
stress. By over expressing the rice hsp100 gene, it was possible to
increase growth under high temperatures. Basmati rice was transformed
with the Arabidopsis hsp101 gene driven by a maize ubiquitin promoter
and first intron and transcription terminated by tnos; it was
accompanied by a hygromycin resistance marker driven by a CaMV promoter
and terminated by tnos. The transgenic rice performed better than the
parent strain in heat and in recovery from heat shock [13].

GM research outpacing safety tests
While the GM rice being researched in India may show some promise in
providing pest and disease resistance, or tolerance to abiotic stress,
it is clear that research has raced ahead of safety considerations. As
rice is consumed as a staple food, any GM rice considered for
commercialization must undergo a thorough pre-market safety assessment
and have its safety proven beyond reasonable doubt.

Some areas of especial concern include the use of Bt biopesticides that
are potentially toxic and allergenic (see "GM rice release in China?",
this series); and the complicated, multiple traits that may be
especially prone to genetic instability through illegitimate
recombination. Furthermore, not only the effects of each of the genes,
but also their combined effects must be adequately tested for safety.



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