Transcript BT202 Fundamental_Genetics

Chapter 12: Transgenic crop plants
Inactivation of a gene (antisense)
Herbicide tolerance
Insect resistance
Other examples
Regulations
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Modification of genetic characteristics

To produce an extra protein
– e.g. Roundup ® Ready Soja
– Bt rice

To stop the production of a specific protein:
antisense strategy
– e.g. Flavr Savr ® tomato
– e.g. virus resistant plants
Flavr Savr ® tomato (Calgene)
Antisense polygalacturonase
(cell wall - degrading enzyme) to
prevent overripening of the fruit
(tomato gene in reverse orientation)
• Zeneca tomato paste first on the
market in US and also in UK in 1996.
• Taken from the market in 1999 due to
negative propaganda in the media.
Antisense strategy
promoter
DNA
coding
sequence
messenger RNA
protein
coding
promoter sequence
ANTISENSE
Not only useful for functional analysis, also for applications
Longer fresh
Tomatoes with less cell wall degration are stronger
and less susceptible to fungal infection.
Anti-overripening
(also with other genes)
Other examples in the
pipeline:
squash, melon,
strawberry, banana,
papaya, etc.
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HT Herbicide tolerant soya or corn or rice
Tolerance to herbicides that are specific for plants
and thus less toxic to animals e.g. glyphosate
(Roundup®) or gluphosinate (Basta® of Liberty®)
HT Roundup ® ready soya (Monsanto)
Glyphosate-tolerant soya
• The herbicide glyphosate blocks EPSP synthase,
an enzyme for biosynthesis of aromatic amino acids
• EPSP synthase of Agrobacterium CP4 is relatively
insensitive for glyphosate
• Monsanto’s transgenic soybean contains :
• P35S - TP EPSPS Petunia - EPSPS (CP4) - 3’nos
Promoter - localisation - GENE – terminator
signal for protein
• This soybean stays as (in)sensitive to other herbicides
as non-transgenic soybean, the only change is its
tolerance to glyphosate by the intorduction of one gene
HT
Plants protected
Herbicide tolerant soya, corn and oilseed rape are
commercially cultivated in the US and Canada
HT
Soya with
Soya without
Herbicide treatment herbicide treatment
`
Bron:
Monsanto
10
HT Herbicide tolerant soybean in the world
US: soya 2 HT % in 1996; 77 % in 2002 (>20 milj ha)
Global: 60% of the
90 M ha in 2005
Argentina:
95% of the
9,6 milj ha in
2000 = HT
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HT
Why use it?
• The farmer
– Less costs
– simpler
• The environment
– Much less toxic for animals
– 10-40% less herbicide needed
– biodegradable
HT
Concerns
• Dependence on chemical herbicides stays
in this way of farming
• “superweeds”
Uncareful use can lead to resistance in
weeds (this can also happen in the
trasditional use of these herbicides or
with other herbicides)
HT
Herbicide tolerant crops for developing countries?
Striga (parasitic plant) on corn  burn the field?
HT
Left: control corn (striga damage)
Right: herbicide tolerant corn, seed treated with
herbicide before planting, no striga damage
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BT
Insect tolerant crops by using Bt
• Bt protein crystal toxic for insect larvae
– Bacillus thuringiensis protein
– Biological crop protection product
– Environmentally friendly
– Toxic for specific group of insects, for
example only for beetles or only for
caterpillars
• Transgenic plant produces Bt-protein
BT
Bt-corn
Bt
control
Control
Bt
Bt
control
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BT
Bt-cotton: biggest Bt success: on average 1.2
million kg less insecticide on cotton in US
BT Bt-cotton in China
• Study on website of isaaa:
www.isaaa.org/kc/Issues/benefits_China.html
• Cotton of Monsanto or CAAS (China
Academy of Agricultural Sciences)
• Grown by 3 million small farmers in
2000 (ca. 10%)
• On average 20-23% lower costs with
Bt-katoen
• 15.000 ton less insecticide (- 47kg/ha)
• Less farmer intoxications with Btcotton:
(4.7% compared to non-Bt: 22%)
BT
Why use it?
• The farmer
– Lower costs for the farmer
– Higher yields
– Less work: no of few spraying needed
• For the environment
– No or low use of insecticides
– Much more target specific than
insecticides
BT
Concerns
• Bt crops may affect some useful insects
– but less than with traditional insecticides
• Large scale cultivation of Bt-crops can
enhance the emergence of resistant insects
www.isaaa.org
Worldwide total GM crops
1 million ha in 1996
28 million ha in 1998
58 million ha in 2002
81 million ha in 2004
90 million ha in 2005
Europe: only some crops are allowed (mainly corn)
Transgenic crops in the field: 90 mil. ha in 2005
18%
54%
12%
8%
1%
4%
USA
Argentinie
Brazilie
Canada
China
Paraguay
India
Zuid-Afrika
Most
important
production
areas
2%
72%
HT
Bt
17%
1%
10%
HT + Bt
andere
Transgenic crops in the field: 90 mil. ha in 2005
72%
17%
1%
10%
The traits in
the transgenic
plants in the
field: mainly
HT and BT
HT
Bt
HT + Bt
andere
Transgenic crops for developing countries
– local crops or cultivars
– relevant characteristics
– preferentially own
technology
– own production
– for example Cornell University
developed
Virus resistant papaya for
Hawaï/Philippines
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Transgenic crops for developing countries
• Besides Bt cotton, China has also developed its
own transgenic herbicide tolerant rice and insect
tolerant rice.
• Kenya is developing its own herbicide tolerant and
insect tolerant corn.
• Mexico has developed aluminium-tolerant corn
• Virus-resistant cassava has been developed
• Fungus-resistant banana for Ecuador/Uganda
(Kuleuven)
• Nematode resistant potato for Bolivia (University
Leeds)
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Transgenic crops for developing countries
Drought tolerant rice
Production of sugar trehalose at drought
stress
Mechanism cfr. other
drought- tolerant
plants
GM
control
BBC nieuws 26-11
PNAS vol.99 p 15898
(2002)
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Transgenic crops
• Transgenic crops can only be grown after a permission
has been given. A technical dossier with all the details of the
characteristics of the transgenic plant and the results of
toxicity test and environmental risk analysis has to be given
to the authorities.
• In Europe the regulations are very demanding and foods
containing ingredients from transgenic crops have to be
labeled. In the US this is only required if the transgenic crop
has a different composition than the non-transgenic crop
(e.g. a different oil composition).
www.aphis.usda.gov/biotech/not_reg.html: list of
commercially grown GMOs in USA
www.environment.detr.gov.uk/acre/market.pdf: list
commercially grown GMOs in Europe
GMO’s in the media: many false messages
• GMO’s are allergenic
• GMO’s make you impotent, make your brain shrink
• Bt corn kills the Monarch butterfly
• Genes from GMO’s spread without control, normal
genes don’t
Many of the other claims are true but also hold for
traditionally bred varieties, for example risks of
herbicide tolerant plants
Transgenic soya
• Herbicide tolerant
• gene can “flow”
• biodegradable
Roundup, low toxicity
• tested in detail before
commercialisation
• modification known
Monsanto
Non-transgenic soya
• Herbicide tolerant
• gen can “flow”
• persistent Synchrony
low toxicity
• no procedure
for commercialisation
• modification unknown
Dupont
Both varieties are sold by
© 1999 Pioneer Hi-Bred International, Inc.
Archer Daniels Midland offers now more money for the non-GMO!!!
Conclusion :
• It is wise to be careful with transgenic plants, to test
them before putting them on the market, but this
testing is thoroughly done.
• Possible risks of transgenic plants have to be
compared with risks also occurring with traditionally
bred varieties and conventional field practices.