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Chapter 12: Transgenic crop plants

Inactivation of a gene (antisense)

Herbicide tolerance

Insect resistance

Other examples

Regulations

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

DNA

promoterpromotercoding

sequence

messenger RNA

proteinANTISENSE

promoterpromotercoding

sequence

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.

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Anti-overripening (also with other genes)

Other examples in the pipeline:

squash, melon, strawberry, banana, papaya, etc.

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®)

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’nosPromoter - 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

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Soya with Soya without

Herbicide treatment herbicide treatment

` Bron: Monsanto

HT

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Herbicide tolerant soybean in the world

US: soya 2 HT % in 1996; 77 % in 2002 (>20 milj ha)

Argentina:

95% of the 9,6 milj ha in 2000 = HT

HT

Global: 60% of the 90 M ha in 2005

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

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Left: control corn (striga damage)

Right: herbicide tolerant corn, seed treated with herbicide before planting, no striga damage

HT

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

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Bt-cornBT

Bt control

Bt control

Control Bt

Bt-cotton: biggest Bt success: on average 1.2 million kg less insecticide on cotton in US

BT

• 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 Bt-

cotton:(4.7% compared to non-Bt: 22%)

Bt-cotton in ChinaBT

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

BT

Worldwide total GM crops

1 million ha in 199628 million ha in 199858 million ha in 200281 million ha in 200490 million ha in 2005

www.isaaa.org

Europe: only some crops are allowed (mainly corn)

Transgenic crops in the field: 90 mil. ha in 2005

18%

12%8%

2%

1%

54%

4%

USA

Argentinie

Brazilie

Canada

China

Paraguay

India

Zuid-Afrika

17%

10%1%

72%HT

Bt

HT + Bt

andere

Most important production areas

Transgenic crops in the field: 90 mil. ha in 2005

The traits in the transgenic plants in the field: mainly HT and BT

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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

GM control

Drought tolerant rice

Production of sugar trehalose at drought stress

Mechanism cfr. other drought- tolerant plants

BBC nieuws 26-11

PNAS vol.99 p 15898 (2002)

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

Both varieties are sold by © 1999 Pioneer Hi-Bred International, Inc.

Archer Daniels Midland offers now more money for the non-GMO!!!

Transgenic soya Non-transgenic soya

• Herbicide tolerant• gene can “flow”• biodegradable Roundup, low toxicity• tested in detail before commercialisation• modification known Monsanto

• Herbicide tolerant• gen can “flow”• persistent Synchrony low toxicity• no procedure for commercialisation• modification unknown Dupont

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.