Ag-Biotech: Genetically Modified (GM) Foods
4/28/04 and 5/3/04

Readings: Web notes only! This will be our LAST topic of discussion!

'GM Foods' (Genetically Modified Foods) or 'GMOs' (Genetically Modified Organisms) are terms you probably hear about a lot in the media. What do these terms mean and how do they affect your life? Really, all crops and foods we eat could technically be considered 'genetically modified' - from their original undomesticated state, by controlled breeding over hundreds and thousands of years... However, when most people say GM Foods or Transgenic Foods they are usually referring to crop plants that have a foreign gene from another organism 'spliced into' into their genome.

How to make a transgenic plant: Plant cells are 'totipotent' - meaning that any 1 cell can be cultured to grow into a whole new plant. Scientists can easily add desired genes (DNA) to a plant cell by either
a) using a common soil bacteria that naturally brings DNA into plant cells (called Agrobacterium) or
b) by literally 'shooting' DNA into plant cells using a high pressure helium 'gun'.

The result: the incoming DNA is 'spliced into' plant's genome, resulting in a transgenic plant carrying one or more new genes that produce desirable proteins.

I. Questions:

II. Why do we need GM crops (do we need GM crops)?
There are
3 main reasons:

1. We need GM crops to protect crops from insect damage:

The European corn borer (ECB), Ostrinia nubilalis [See this week's Good For!] is the most damaging insect pest of corn throughout the United States, causing well over $1 Billion dollars of damage yearly to corn in the US. Other Lepidopteran insects (caterpillars that become butterflies and moths) like corn rootworm, cotton bollworm, tobacco budworm, etc., cause combined damages of over $7 Billion dollars yearly in the US. That's a lot of damage by some little bugs!!!  

One way to control Lepidopteran pests is to use the natural insecticide Dipel [See this week's Good For!]. Dipel is a 'friendly' insecticide that is literally a freeze-dried, naturally occurring soil bacterium, Bacillus thurengiensis (Bt), that makes a protein, called the crystal protein, that is toxic to Lepidopterans (and harmless to other insects, wildlife, and humans). However, Dipel is pretty ineffective against the Eurpoean Corn Borer because it only reaches the outer parts of the plant where it is sprinkled on the leaves. The Eurpoean Corn Borer, true to its name, can bore into the developing corn ear and destroy it even if there is Dipel on the leaf of the corn plant... Thus, Dipel is pretty ineffective against ECB because it doesn't reach the insects that have bored inside the stalk.

The solution: Scientists created a genetically modified plant that carries the gene for the Bt crystal protein toxin. This cry gene (crystal protein gene) was introduced into a plant cell and an entire plant was grown up that carried the gene - and made the protein - in every one of its cells. This means that every plant cell - including those inside the husks - those yummy corn kernels - is now able to make the Bt crystal protein toxin...loook out Eurpoean Corn Borer!

Today, Bt-hybrids of corn, tobacco, cotton, potatoes, and other crop plants have been genetically engineered to contain cry genes, which produce the crystal proteins in the plant's leaves, stalk and pollen. Once eaten, the crystal protein destroys the insect's gut lining.

Monsanto makes MaisGard and YieldGard Bt corn, Bollgard Bt cotton seed, NewLeaf Bt Potatoes, plus other Bt products; other companies make YieldGard Insect resistance (ECB) - DeKalb; Maximizer Insect resistance (ECB) - Novartis/Northrup King, NatureGard Insect resistance (ECB) - DowAgrosciences / Mycogen Seeds


2. We need GM crops to lower herbicide use:

Weeds (ie plants growing where they are not desired) can reduce the yield of crops by up to 50% - and cause millions of dollars in losses to farmers. There are a lot of herbicides available that are selective - they kill weeds, but leave grasses like corn alone - but many are really nasty and toxic: they do not break down quickly, they leach into groundwater, etc.  

Herbicides that are more 'friendly' like RoundUp are great, but they are non-selective - you can only spray the weed and not the crop - very tricky and time consuming in a huge corn field.  

The solution: Create a plant that is genetically resistant to (unaffected by) RoundUp - then spray the whole darn field with the friendly herbicide RoundUp - only the resistant plants - called "Round Up Ready" will survive!  

Remember Good For 12? - RoundUp works by inhibiting an enzyme that only plants and bacteria have, called EPSP synthase. This enzyme is crucial for the plants to make proteins. In the early 1990's, scientists at Monsanto isolated a version of this protein that was naturally resistant to Roundup - ie it still functioned to make proteins and even in the presence of glyphosate

In 1994, a patent was granted on this mutant EPSP synthase gene: United States Patent 5,633,435: Glyphosate tolerant EPSP synthase (ie RoundUp resistance) to Monsanto. This mutant gene made a protein was still able to make amino acids even in the presence of glyphosate!! An organism that carried this mutant EPSP synthasse would be RoundUp resistant!!!

In 1996: the first plants genetically engineered with tolerance to Roundup hit the market. This "In plant" herbicide tolerance is named RoundUp Ready by Monsanto.

What is the end result? Farmers plant Round Up ready seeds, and spray their weedy fields with the friendly RoundUp herbicide - death to weeds, crops remain healthy. (Big Bonus $ for Monsanto: Everyone who wants to use this system has to now buy Two Monsanto products!!! RoundUp Herbicide and RoundUp Ready Seeds!)


3. We need GM crops to increase food production and quality:

A. Increase Food Production: The world population is growing at over 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. Higher Yield: Monsanto's YieldGard (Bt) plants outperform other corn varieties in terms of yield - bushels / acre. Higher Yield = can feed more people / acre. Farmers rely on yield to make a profit for that year, and varieties of crops that are high yield are very desirable to farmers. In addition, while we are not NOW in dire need to maximize crop yield to feed people on Earth (see Warm Up question..), we may get to a point in the future where growing enough food for everyone on the planet is a necessity

B. Increase Food Quality: On May 18, 1994 the Food and Drug Administration announced the arrival of Calgene's FlavrSavr tomato, the first transgenic food, to the supermarket shelves. FlavrSavr had undergone a decade of testing, costing $525 million, before being approved safe by the FDA. The FlavrSavr was designed by scientists who were trying to overcome an annoying problem: mealy, pinkish-red, flavorless winter tomatoes!! Store-bought tomatoes (even in the summer) are typically picked when green, hard, unripe, and NOT sweet just so they will survive their trip to the grocery store intact; once there, they are treated with natural plant ripening hormones so that they turn somewhat red, with a somewhat sweet taste...but nothing like the real yummy garden tomato!!! To the rescue: The FlavrSavr - "Engineered to remain firm even as it turns red and ripe, FlavrSavr provides summertime taste year round". Although delicious, the FlavrSavr suffers from consumer resistance, high price, poor marketing and PR, and a boycott by chefs..... Calgene, heavily in debt before the tomato hit the market, declares the FlavrSavr dead on the vine in 1997. [Image]

C. Nutritionally enhanced crops: Over ~500,000 children / year go blind from a lack of Vitamin A in their diet, and close to ~ 5 million people / year die because of vitamin A deficiency (VAD). VAD can easily be eliminated by eating a daily amount of Beta carotene - the vitamin found in carrots and other orange vegetables that is converted in your body to Vitamin A. (didn't your mom always tell you that carrots were good for your eyes - well, she's right!). In 2000, a scientist named Ingo Potrykis reported that he had made transgenic rice that contained 4 B-carotene genes from Daffodils and other species. The grains of this rice are a beautiful yellowish-orangeish-gold color and contain natural B-carotene. He patented his product, Golden Rice, and several companies (including Monsanto) are developing it for market FREE for developing countries. Science, 287: 303 (2000) Ingo Potrykis. Higher nutrition = can help people lead healthier lives.

Golden rice is a wonderful product, and just the type of GM crop that appeals to the public, but there are a few drawbacks:
- A person would have to consume POUNDS of rice a day just to get the recommended daily allowance of B-carotene/vitamin A currently made in Golden Rice.
- B-carotene is fat-soluble vitamin, and starving people usually don't have enough body fat to effectively bring the B-carotene into their bodies to turn it into vitamin A
- alleviating 1 vitamin deficiency is a start, but a multivitamin's worth (and more) of nutritional deficiencies need to be corrected in people living on a cup of rice a day (or less...) Snif
However: Even with drawbacks, still a great idea for the future of GM crops!!!

II. Seeds of Change: How widespread are GM Crops in the US?

1990: First fertile transgenic maize (Bt corn), DeKalb Genetics.
Genetically modified (GM) crops hit the market 'big time':

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

GM food on supermarket shelves - Starting in 1999

2000 - 2004: Percentages increase even more (but decrease for corn):

III. Issues surrounding GM foods:

1. Development of insecticide-resistant Lepidopteran insects

In any group of organism that are given a poison (like bacteria and antibiotics), there are bound to be a few who survive the poison due to a slight genetic advantage (natural selection in action). What happens when the ECB develops resistance to Bt and then passes the resistance on to their descendants???

EPA's Bt plan - March 2000 Refuge strategy. Growers who plant Bt hybrids must also plant refuges (blocks of non-Bt corn). The refuge supplies a source of moths that are not exposed to Bt corn to mate with those that have resistance to Bt. That mating should delay resistance for 20 - 50 years, extending the lifespan of this crop.


2. Non-target insect damage: Are friendly insects in the environment harmed by Bt-crops?

A report by Losey et al (1999) in Nature showed that Monarch Butterfly caterpillars (Lepidopterans) are also hurt by Dipel, and by Bt-corn pollen...People are very sensitive to the environmental image of monarch butterflies, and scientists, environmental groups, and the general public because VERY concerned about Bt-crops. An investigation followed: .

"9/20/00 WASHINGTON (AP) - "The US EPA issued a report (PDF)
Biopesticides Registration Action Document: Bt-plant Pesticides stating that Bt crops that have been genetically engineered to kill insects pose "no unreasonable adverse effects"to Monarch butterflies or to any other animal. A Cornell University study found the pollen was toxic to Monarchs in the laboratory. The butterfly feeds on milkweed, which often grows around corn fields. Although pollen from GM corn can kill Monarch butterflies in large doses, there is probably little risk to them around corn fields. Evidence indicates that the corn may even turn out to be beneficial to the butterflies because farmers are using less chemical pesticides, EPA said. The study also affirmed that the crops approved for human consumption are safe to eat."

Monarch and Bt-Corn: Questions and answers.


3. Consumer Safety / Food Safety

How is transgenic food approved in the US?

USDA: Grants permission to test GM crops
FDA: A voluntary step (currently, stay tuned)! FDA policy does not consider GM foods to require a food additive testing procedure - but they would like developers to consult with them before marketing.
EPA: They approve whether the product is safe for human consumption and environmentally safe

StarLink Taco Shells (Aventis) were pulled from the shelves lin October 2000 because they contained a crystal protein cry gene that had beed tested and approved by the EPA as safe for cattle feed, but had not yet approved it for human consumprion. Baaad mooove, Aventis....


4. Consumer confidence / Food labeling:

Want to read more? Is eating food from transgenic crops a health hazard? and Waiter, there's a gene in my food!

So far, it does look like the positive effects of GM Crops outweigh the negative. Careful monitoring will be needed as more and more GM crops and foods come to market. In the meantime, eat up!


1. What are the 3 main reasons why GM Crops are produced?

A. What is Bt toxin, and what is Bt-corn? (please read Good For #11 as well)
B. What is RoundUp, and what does does RoundUp Ready mean? (Please read Good For #10 as well)
C. What is Golden Rice?

2. What percentage of corn, soybeans, and cotton in the US were genetically modified in 1999? in 2000?
3. What is being done to delay resistence of Lepidopteran insects to Bt?
4. What is the effect of Bt on non-target insects like monarch butterfly caterpillars?
5. What role do the USDA, FDA, and EPA have in the regulation of GM foods? Why were the StarLink taco shells remmoived from supermarketshelves?
6. Why aren't GM foods in the US labeled as GM foods?