Ag-Biotech: Genetically Modified (GM) Foods
4/28/03 and 4/30/03

Readings: Web notes only! This will be a long one, but we will take two days to get through the material!
Note: If you have not done so already, please read the two Good For's: #10 (RoundUp) and #11 (Dipel). Material for the test will come from these two readings as well as the lecture notes!

'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.

I. Questions:

II. How do scientists 'splice genes' from one organism to another?

We are not doing justice to the amount of time we could spend on recombinant DNA technology, but here's the bottom line. Certain enzymes (naturally found in bacteria, and first discovered by scientists in the 1970s), are naturally able to cut ( or 'restrict') a piece of double-stranded DNA with a very specific nucleotide sequence (like the DNA sequence GAATTC), leaving unpaired nucleotides at the cut site called 'sticky ends'. Scientists have now isolated hundreds of different restriction enzymes. If TWO pieces of DNA (like a piece from human and a piece from bacteria) are cut with the SAME enzyme, they will both have matching 'ends' and can be joined together in a test tube, creating re-combinant DNA (DNA combined from two different species). [Stanford University had the patent on Recombinant DNA teachnology until 2000 - they made hundreds of millions of dollars off this basic teachique!]

What can you DO with a piece of recombinant DNA? IN the case shown below, the human insulin gene was put into a bacterial chromosome, re-introduced into bacteria, and the bacteria them made the human insulin protein just by regular old transciption and translation. Many drugs (Epogen, Herceptin) are made this way. Many scientists syudy genes of interest by putting them into a new organism and observing the effect. Once the organism carries this recombinant gene, they are called "trans-genic". Transgenic mice have been made that allow scientists to study human diseases like obseity, diabetes, etc.

Recombinant DNA can be made from any two species - since all living organisms share the same universal genetic code, the foreign piece of DNA is treated like any other piece of DNA in the cell.

Introducing the recombinant DNA into the host organism differs for different organisms - Bacteria will quite easily take up foreign DNA just from bathing in a liquid solution containing calcium; animal cells will take up foreign DNA when subjected to pulses of electricity ('electroporation') or by using animal viruses, and plant cells, with their rigid cell walls, can be induced to take up DNA when the cells are literally SHOT with DNA fired from a Helium Gun!

How to make a transgenic plant:

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

1. To protect crops from insect damage:

The European corn borer(ECB), Ostrinia nubilalis, 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 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!!!  

Control of the ECB and other Lepidopteran pests can be done with Dipel (see Good For 11), but, Dipel only reaches the outer parts of the plant where it is sprinkled on the leaves. The ECB can tunnel into the developing corn ear and destroy it even if there is Dipel on the leaf of the corn plant... Prior to 1990, Dipel was pretty ineffective against ECB because it couldn't reach the insects inside the stalk.

The solution: create a genetically modified plant that carries the gene for the Bt crystal protein toxin - the Bt toxin gene. 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. (Plant cells, by the way, ARE totipotent!) This means that every plant cell is now able to make the Bt crystal protein toxin...loook out bugs!

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

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2. 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!)

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3. 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 (2/2001). Higher Yield = can feed more people / acre.z

B. Increase Food Quality: An idea that failed...because the public was not ready for it: ­ On May 18, 1994 the Food and Drug Administration announces 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. 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 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 each year go blind from a lack of Vitamin A in their diet (or Beta carotene - the vitamin found in orange vegetables), and close to ~ 5 million people / year die because of vitamin A deficiency. In 2000, a scientist named Ingo Potrykis reported that he had made transgenic rice that contained Vitamin A (B-catrtoene) genes from Daffodils. He patented his product, Golden Rice, and several companies (including Monsanto) are developing it for market. Science, 287: 303 (2000) Ingo Potrykis. Higher nutrition = can help people lead healthier lives.

Note from Dr. Marrs: "It is a myth that world hunger is caused by a scarcity of food" Economics, politics, war, poverty, etc...are the root causes of why 40,000 people die every day of starvation. If you can't get access to food where you live, or you don't have the money to pay for the food that is there, it does not matter how much technology is available to increase food production or nutrition !!!! Feel like getting more involved in this? = Oxfam International.

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

1990: First fertile transgenic maize (Bt corn), DeKalb Genetics.

1996: 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 - 1999

2000 - 2002: Percentages increase even more (but decrease for corn):

IV. 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. What happens when the ECB develops resistance to Bt and then pass their 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.

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2. Non-target insect damage:

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...It is true that Bt-corn pollen can kill caterpillars, but....

"9/20/00 WASHINGTON (AP) - "The US EPA issued a report 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.

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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....

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4. 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!

Objectives:

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?