Genetically Modified Crops:

Boon or Bane?

Dr. Gina Malczewski

Dr. Bob Kremer, USDA August 15, 2013

GMO: History and Status • 1974: Monsanto introduces Roundup • 1980: Supreme Court says genes can be patented • 1994: Flavr Savr tomatoes (delayed softening), Calgene • 1996: Roundup ready soybeans • GMOs not allowed in certified organic food • US 2012: GM corn=88%, GM cotton=94%, GM

soybeans=93%. 84 million cares of corn, 73 million of soybeans (EPA)

• Some GM foods: corn, animal feed, oils, soybeans, tomatoes, sugar beets(?), Golden rice (?), potatoes, squash, salmon (coming?)

• Europe buys only 2% of our grain (no GMO allowed), but has no rules on GMO content in processed foods

From Nature May 2, 2013

From Nature May 2, 2013

Some abbreviations

• DNA: deoxyribonucleic acid (genetic material)

– Bases

– Phosphate (P) backbone

• RNA: ribonucleic acid (cell machinery)

• AA: amino acid, building block of protein

To understand genes…

https://familysearch.org/learn/wiki/en/File:DNA_Double_Helix.png

http://www.biology.arizona.edu/biomath/tutorials/linear/linearfunctionapplication/dnamelt.htm

http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/B/BasePairing.html

T A

C G

Genes and Genetics

• Chromosomes are complexes of genes and proteins

• Genes are sequences of DNA; they usually code for proteins that do much of the everyday work in cells

http://www.astrobio.net/amee/summer_2008/Features/images/SeeingLifeInViruses-DNA.jpg

http://www.brooklyn.cuny.edu/bc/ahp/BioInfo/graphics/GP.GeneticCode.GIF

•Different genes have different lengths and sequences depending on what they code for •To study genes, special enzymes that clip DNA at specific places can be used to cut up DNA. The pieces can then be analyzed for what they produce by splicing them into other DNA molecules that are being “transcribed” and “translated”

Bacteria are Different

• No nucleus, no chromosomes

• 1 long strand of DNA and sometimes extra small “circles” called plasmids

• Code for special genes that give an advantage

• Plasmids often carry genes for antibiotic resistance, used as markers for successful gene transfer

http://en.wikipedia.org/wiki/File:Gene2-plain.svg

How Genes Work in Animals and Plants

3 bases are read together to code for ONE Amino Acid. At least one string of AAs is needed for a protein

Agricultural Manipulation through History

• Gregor Mendel: Crosses of plants to obtain more desirable traits

• Farmers save seed from best plants to optimize desirable traits

• Seeds can be exposed to radiation or chemicals to induce changes to DNA

• Plant cell protoplasts are fused to make hybrids that hopefully express both sets of genes

• Cultivating land in certain ways, removing natural vegetation, can be done without oversight

So how do you find the gene for the trait you want?

• Cut and splice DNA pieces into plasmids, allow them to replicate, and look for product or new ability

• Look for “survivors” in a natural selective environment, then sequence DNA and find what’s different

• Sequence desired protein and figure out possible DNA sequence

http://jan.ucc.nau.edu/~lrm22/bio300/lecture_notes/lecture3/restriction_enzyme.jpg

What’s next?

• Purify gene (if bacterial may have to change it slightly for plants)

• Get it into plants: some possibilities – already there?

– Plasmids by electroporation

– “Gene gun”

– Agrobactrium tumefaciens

• Plants must survive and reproduce, passing along the new DNA

Agrobacterium tumefaciens

These bacteria are already known to invade plant cells and part of their DNA joins with the plant DNA

The Arguments PRO

• Increase in some nutrients; drugs?

• Better yields; more food

• Less pesticide used

• “no till”cultivation prevents soil erosion. Decrease in use of fossil fuels

• Potential for drought resistant plants or those adapted to harsh environments

• Tested to best criteria—normal food not tested

• No harm shown in 20 yr of use

CON

• Techniques are “crude, inexact and unpredictable”

• Monsanto

• CMV viral promoter; increase copies of other genes?

• Allergies? (Brazil nut story)

• Interspecies gene transfer

• Antibiotic resistance transferred to humans?

• Contamination miles away

• Small farmers can’t afford

• Seed control

• Resistance/opportunistic pests

May, 2013:

Advocates say that GM crops have increased agriculture production by nearly $100 billion and prevented nearly 500 million kg of pesticides from being sprayed since the technology was first commercialized nearly two decades ago. GM cotton in China has helped farmers increased yields by nearly 6% since 1997 and reduced the use of insecticides by around 80%.

Introduction of herbicide-tolerant cotton saved 15.5 million kg of herbicide

between 1996 and 2011—a 6.2% reduction from what would have been used on conventional cotton.

Read more: http://science.time.com/2013/05/14/modifying-the-endless-genetically-modified-crop-debate/#ixzz2bXBD805a

Read more: http://science.time.com/2013/05/14/modifying-the-endless-genetically-modified-crop-debate/#ixzz2bXAoKyCn

From Nature May 2, 2013

5-enolpyruvylshikimate-3-phosphate (EPSP) synthase

Round-up: Glyphosate

Glyphosate is a competitive inhibitor. This enzyme is needed for aromatic amino acids that make proteins; without them, ALL PLANTS DIE . Humans unaffected by this; we get these AAs from ort diet.

•broad spectrum •low toxicity •low persistence, breaks down readily with sun and rain

•Top: Lesser cornstalk borer larvae extensively damaged the

leaves of this unprotected peanut plant.

•Bottom: After only a few bites of peanut leaves of this genetically

engineered plant (containing the genes of the Bacillus

thuringiensis (Bt) bacteria), this lesser cornstalk borer larva

crawled off the leaf and died. http://en.wikipedia.org/wiki/File:Bt_plants.png

Bt 1000X; http://textbookofbacteriology.net/Anthrax.html

Bt crops •Protein toxins made by Bacillus thuringiensis (Bt) used in organic farming for over 50 years •1995: Bt potato strain •Bt corn and cotton introduced in 1996 •1997: seven times less spraying for tobacco and cotton budworms •1998: Pusztai study of Bt potatoes in rats •1999: Monarch butterfly study at Cornell

Currently: 2012http://www.motherjones.com

/tom-philpott/2012/03/researchers-gm-crops-are-killing-monarch-butterflies-after-all

http://www.inspection.gc.ca/plants/plants-with-novel-traits/general-public/monarch-butterflies/eng/1338140112942/1338140224895

…Monarch butterflies exposed to Bt corn in the environment are not subjected to any significant risk.

Showa Denko Tryptophan 1989

• Japanese company supplies US with AA tryptophan as nutritional supplement (exempt from FDA rules)

• Changed to GE bacterial source. 2000 people sickened, 37 died from EMS (eospinophilia myalgia syndrome). Filtration issue? Contaminant from bacteria?

• Smith MJ, Garrett RH (2005). "A heretofore undisclosed crux of eosinophilia-myalgia syndrome: compromised histamine degradation". Inflamm. Res. 54 (11): 435–50 (2005); Part II in 2007

Pesticide Use

• Impacts of genetically engineered crops on pesticide use in the U.S. -- the first sixteen years, Charles Benbrook Environmental Sciences Europe 2012, 24:24 – 527 x 106 lb ↑ herbicides use in US 1996-2011 – 123 x 106 lb ↓ pesticide use in US

• BUT—be careful to survey and interpret carefully: – herbicide use data are difficult to obtain, and are not

reported separately for conventional and GMO crops – Data were interpolated in every case because of missing

points; as many as six of 17 points. In one case last 5 points estimated http://weedcontrolfreaks.com/2012/10/do-genetically-engineered-crops-really-increase-herbicide-use

Other issues • Brazil nuts, 1996

– Allergenic parts of used for splicing to increase protein in soybeans

– Never commercialized

• 1998: Pusztai Bt potato studies in rats

– Diet issues

– Repeat Dutch study

• Impact on farmers: Seeds cost more, can’t save.

Conclusions

• GMO use in food has become a contentious issue. Both sides have played with facts, and science has not had much visibility in all the hype.

• There appear to be advantages to GMO foods, and there are also uncertainties.

• From Sci Am (Nature) 5/1/13: Tidy stories, in favor of or against GM crops,

will always miss the bigger picture, which

is nuanced, equivocal and undeniably

messy. Transgenic crops will not solve all

the agricultural challenges facing the

developing or developed world… but

vilification is not appropriate either. The

truth is somewhere in the middle.