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AgBiotech 1: Joe Petolino, Dow Agrosciences
October 30, 2007


I. Seeds of Change:

1980: First transgenic plants. The Birth of Plant Biotech. Mary-Dell Chilton, Wash U. (and 3 other groups almost simultaneously) showed that the soil bacterium Agrobacterium tumefaciens can insert its Ti plasmid DNA into tobacco, Nicotiana plumbaginifolia. Shortly after that, work by Chilton (and other groups) showed that the bacterium could be used as a gene vector, creating tobacco plants that were kanamycin resistant. Cool.

1990: First fertile transgenic maize (Bt corn), DeKalb Genetics.
[PDF] Fertile Transgenic Maize - a great paper if you get a chance!!!!!

 1994-1997: The tragic story of the FlavrSavr, the first GM food licensed by the FDA for human consumption.

1996: Genetically modified (GM) crops: Bt-corn and RR soybean:

Mycogen Corp / Ciba Seeds is the first company to market hybrid Bt-corn (ECB).

Monsanto introduces Round-up Ready Soybeans and BollGard (Bt) cotton.

1999: GM crops cover 25% of US Cropland - over 98 million acres

~37-45% of all corn is genetically engineered [Image]

~47-55% of all soybeans are genetically engineered

~48-50% of all cotton is genetically engineered

Over 50 GM crops have been approved by the USDA - potatoes, tomatoes, melons, beets, strawberries, rice, wheat, apples, cucumbers, etc.

2003: GM crops cover 40% of US Cropland ~ 110 million acres, and 167 million acres worldwide (Argentina is next biggest grower of GM crops). Today (Summer 2007...)

~40% of all corn is genetically engineered

~80% of all soybeans are genetically engineered

~75% of all cotton is genetically engineered

II. Questions for this week and next:

What are GM crops and how do you make them?

Why do we need GM crops? Three reasons.

What Biotech companies are at the forefront of Ag-Biotech Crop production? [Image]

What Regulatory Processes exist for GM Crops?

What are the issues surrounding GM Foods - real or imagined?

    Environmental Issues

    Health Issues

    Consumer Issues

III. What are GM crops? Really, all crops and plant foods we eat are technically GM - 'genetically modified' - from their original undomesticated state, by controlled breeding over hundreds of years.

 

A 'true' GM plant, or transgenic plant, however, contains a gene or genes from another organism stably and heritably inserted into their genome via genetic engineering rather than via pollination. Transgenic plants are are what many people mean when they talk about GM foods or GMOs. We will use the terms (GM / GMO / transgenic) to refer to those plants with a foreign transgene inserted.

 

How do you make a transgenic plant? A great review of how to...

(1) Identify and Locate genes for plant traits: insect resistance, herbicide resistance, yield potential, stress tolerance, new chemical products etc"

(2) Design genes for insertion (transgenes)

Marker: Kan, Bar Promoter: CaMV 35S, Cab Transgene, Temination


(3) Transform plant tissue; Three main methods:
---> Agro (basic procedure, Chilton et al., Fraley et al)
---> Gene Gun: John Sanford, Cornell (basic procedure, Hasegawa et al., Beachy et al., 2004 review article)
---> Whiskers (patent to Dow Agrosciences)


(4) Select transformants and regenerate them into plants

IV. Why do we need GM crops?

"Goals of Agricultural Biotechnology: In general terms, these goals fall into two major categories:

  1. Improving crop performance in the field (Input Traits) - These matter to...
    o Examples: Virus, Insect, Herbicide, Fungal resistance, Environmental stress tolerance, YIELD!!!
  2. Developing new products with enhanced value (Output Traits) - These matter to...
    o Examples: Nutritional/Health benefits, Shelf life, novel products, edible vaccines or other medicines..
  3. Input vs. Output Traits (examples).

Three specifics:

1. To protect against insect damage: The European corn borer(ECB) causes well over $1 B of damage yearly to corn in the US. Other insects like corn rootworm, cotton bollworm, tobacco budworm, etc. cause combined damages of over $7 B yearly in the US.

  • Bacillus thuringiensis is a gm+ soil bacterium that produces an insecticidal crystal protein from the cry genes (over 100 genes in different strains)
  • Bt crystal proteins are toxic to Lepidopteran insects such as the ECB and other related pests. When ingested, the Bt crystal toxin is activated by enzymes in the insect's gut. The activated toxin attaches to specific gut receptors, destroys cells in the gut wall, puncturing the gut and poisoning the insect. [Image]
  • Bt-toxin (example: Dipel) is an 'environmentally friendly' insecticide used for ~40 years in both conventional and organic farming. Dipel is simply freeze-dried Bt, containing lots of crystal protein.
  • Prior to 1990, Bt was pretty ineffective against ECB - because it couldn't reach the insects inside the stalk.
  • Solution: "In Plant Protection"- Isolate the cry genes from bacteria, and introduce into corn plants (early '90s) = transgenic Bt-corn, followed by Bt-cotton, etc. These GM crops make the cry proteins in each and every cell of the plant. Reduces or eliminates the traditional spraying of Bt in the field and outperforms spraying with Bt.

2. To lower herbicide use: Weeds (ie plants growing where they are not desired) reduce the yield of crops in three ways:

  • Weeds can reduce yield - the 'bottom line' for farmers - up to 50% by (1) competing with the crop for water, light and nutrients, (2) interfering with crop harvest, and (3) contaminating harvested seeds or products with weed seeds and toxins.
  • Weed Control...RoundUp (glyphosate), one of the world's most popular and 'friendly' herbicides, binds to and inhibits EPSP synthase, involved in the production of aromatic amino acids. All plants and bacteria use EPSP synthase to make aromatic amino acids, so all plants (& bacteria) are sensitive to RoundUp.
  • 1985: Agrobacterium mutant found that differed from the wild type by 1 amino acid and did not have affinity for glyphosate (Luca Comai et al.). Bacteria with this mutant EPSP synthase continue to make amino acids even in the presence of glyphosate.
  • 1994: Well, then, let's put it into plants! United States Patent 5,633,435: Glyphosate tolerant EPSP synthase = RoundUp resistance: to Monsanto
  • 1996: plants genetically engineered with tolerance to herbicides (ie Roundup). "In plant" herbicide tolerance = Round Up Ready
  • September 2000: Patent on RoundUp expires! But new formulations already on the market.
  • September 2002: Do farmers love RR plants...or not? The Corn and Soybean Digest says yes!

3. To increase food production and quality: The world population is growing at ~200,000 people per day = well over 1 million people per week. Additional people need additional food (etc..). If more food, or more nutritious food, can be produced on the same land, can feed more people on the same land.

A great list of Transgenic Crops on the Market
Notable Discontinued Transgenic Crops
Possibilities for Future Transgenic Crops

Objectives:

  1. Compare and contrast the mechanisms of transformation for monocot and dicot plants. What is Agrobacterium? Kanamycin?
  2. Know the 1999 and most current (2006/07) figures for GM crops in the US (corn, cotton, soybean)
  3. Explain how insect resistance is engineered into plants.
  4. What is Dipel? Bt? What is the cry gene / protein? What does this protein do to Lepidopteran insects?
  5. Explain how herbicide resistance is engineered into plants.
  6. What is EPSP synthase? What is RoundUp?
  7. How do GM crops with herbicide resistance benefit the farmer? (how does it benefit Monsanto?!)
  8. What is Golden Rice, and what is its promise for the future? What are some of the concerns? What transgenes do these GM rice strains carry?

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