GM Crops, from Science to Politics
L. Andrew Staehelin
Department of Molecular, Cellular and Developmental Biology
University of Colorado, Boulder
Forum on Science, Ethics & Policy (FOSEP) lecture
November 14, 2013
QUESTION:
Who has never eaten a taco or a
burrito?
Presentation topics
• Feeding the world – the big problem
• Why are GM crops controversial?
• The science behind genetically engineered crops
• Examples and properties of GM crops
• Golden Rice
The big problem – how can we feed the world?
my birth
Industrial revolution
Agriculture - The cultivation of land to produce
crops for human consumption and use
• Foods
Proteins, Starch, Oils, Micronutrients
• Industrial materials
Starch, Fibers, Oils
• Pharmaceuticals
Natural Chemicals (plant-derived drugs),
Vaccines, Antibodies, Protein Drugs (insulin)
How will we feed the growing world
population?
Agricultural challenges
• less agricultural land (urbanization, salination,
desertification)
• less water (competing uses, contamination)
• global warming
• the GREEN REVOLUTION has run its course
wheat
The Green Revolution was
driven in part by the
introduction of genes for
dwarfism: shorter stems ->
more seeds/fruits.
Can organic farming feed the world?
NO!
• Why did farmers abandon organic farming 100years ago?
• Organic farming is between 3% and 55% less productive
than traditional farming. It could not even feed the current
world population.
• Organic farming is much more sensitive to environmental
challenges (insects, pathogens, drought). Thus, its
productivity is more variable than traditional agriculture.
• Conclusion: organic farming does not provide an option for
feeding the world now or in the future.
How can we produce more food?
Agricultural changes
• improve cultivation methods (fertilizer and water use)
•
improve storage and transport
Biological improvements
• reduce crop losses during/after cultivation due to insect pests,
pathogens, heat, water and salinity stresses
• increase productivity of plants (more seeds, bigger fruit)
• improve nutrient value (increased content of desired products,
e.g. protein to reduce need for meat)
Biological improvements require CHANGES IN GENETIC MAKEUP!
Methods for changing genetic makeup of crop plants
Traditional breeding
• limited in scope to gene pool of given plant
• time consuming (~10 years) due to long generation times
Mutagenesis – radiation, chemical, tissue culture growth
• results unpredictable; limited in scope
Genetic engineering
• can utilize genes of all organisms (cis-genic, trans-genic)
• can add new genes or suppress the expression of existing
genes (silencing)
• more precise and faster than traditional breeding
Why should we produce and cultivate GM crops?
Educational Challenge for Scientists
Eurobarometer 2003 Survey
Is the following statement true?
“Ordinary tomatoes do not
contain genes, while genetically
modified tomatoes do.”
Only 36% of 17,000 respondents
across 17 EU countries correctly
identified this statement as false.
• GM crops and foods are controversial
• What are the reasons cited by anti-GM
activists for opposing GM crops and foods?
CLAIM: GM crops are dangerous and and GM foods unhealthy
GM crops have been grown for >20 years. Not a single death has been traced
to the consumption of GM foods.
Organic foods: during past 10 years hundreds of people have died and
thousands of people have been hospitalized after eating organic foods.
CLAIMS by anti-GMO crusaders:
“The science has not been done” (Charles Benbrook,
anti-GMO expert who has testified for a ban on GM
crops in Boulder County)
“The research on GMOs is scant” (Tom Philpot, Mother
Jones)
“GM foods should be a concern … because they are
not tested” (Organic Consumers Association)
Test: How many GM food and environmental safety
studies have been published in the past ten years?
Test results
Between 2002 and October 2012
scientists have published 1783 studies about the safety
and environmental impacts of GMO foods and crops.
No significant hazards have been detected.
Nicolia et al. Critical Reviews Biotechnology, 2013
Personal observation: the publications claiming that GM
foods and crops are dangerous are generally of poor
quality and lack critical controls.
CLAIM: The planting of GM crops has not reduced insecticide
use
Test: Bt corn planting versus insecticide use
Insecticide use
EPA data; Science 341: 731, 2013
CLAIM: Only farmers in developed countries benefit from GM crops
CLAIM: Monsanto controls the GM crop business
Ringspot virus-resistant papaya trees developed by Hawaian scientists
Diseased, non-transformed trees in foreground, and healthy, transgenic trees behind.
Crop protection against APHIDS– a new approach
FACT: Aphids cause huge crop losses (cereals, fruits)
Background information:
• When attacked by a predator, aphids emit a volatile chemical, EBF,
that causes other aphids to flee.
• Some plants (hops, mint) have evolved the same system to protect
themselves against aphids, i.e. they produce EBF when attacked.
Protection of wheat against aphids:
Scientists at the John Innes Laboratory, England, have transferred the
mint gene for EGF into wheat and the aphids stay away.
Question:
Why should this crop protection system not be used by organic
farmers? It’s natural and does not involve pesticides.
Why do the Organic Food Industry and Greenpeace
continue to agitate against GM crops and foods?
MONEY!
The $30 billion/year Organic Food Industry justifies
its higher prices by not selling GM foods (profits!).
For the $300 million/year Greenpeace corporation
the destruction of GM test plots is a cheap way to
get news coverage and to raise funds.
The Scientific Basis of Plant Genetic Engineering
Lateral gene transfer, the mechanism of DNA transfer
exploited in genetic engineering, is natural, predates
sex, and is used by many organisms.
Examples:
• transfer of antibiotic resistance between bacteria
• 8% of human DNA is viral DNA
• transferring foreign DNA into a plant cell is as easy as dipping
a shoot into a DNA solution and collecting transformed seeds a
few weeks later
Agrobacterium tumefasciens – a soil bacterium
DNA
Ti plasmid
Ti plasmid contains 25 vir genes, which can be injected into plant cells
by bacterium
T-DNA sequences in plasmid allow for the insertion of plasmid genes
into plant cell DNA
Vir genes code for enzymes for producing
• plant hormones (auxin, cytokinins) that promote uncontrolled cell
divisions (tumors)
• unusual amino acids (opins) that provide food (N- and C-sources)
for the bacteria
The Agrobacterium transformation system
Modification of Ti plasmids for transformation experiments
•
removal of genes coding for opin synthesis enzymes
•
removal of genes coding for hormone synthesis enzymes
(no tumor formation)
•
insertion of desired gene plus selection marker gene into
emasculated Ti plasmid
Production of a transgenic plant
Plant cell
Adoption of GM Crops
European corn borer protection by Bt cry-protein
Bt Corn
Non-Bt Corn
European corn borer
Sources: Monsanto, Clemson University
European corn borer
European corn borer damage to corn kernels:
Bt-Maize v. non-Bt-Maize
Fusarium molds (arrow) produce fumonisins, highly toxic chemicals,
that cause cancer and spina bifida babies
Damage from corn rootworm feeding - can be
controlled with Bt protein expression
Sources:
USDA, Iowa State Univ.
Bt crops
Crops: corn, cotton, soybeans, potato, tomato
Mode of action of Cry proteins
• Insect guts have alkaline pH, which converts the Cry protein to a
membrane pore-forming toxin
• In acidic intestines (mammals, birds, fish) the Cry proteins
remain inactive and are digested
Benefits of Bt crops
• Very effective for combating European corn borer, cotton
bollworm, and corn rootworm
• Farmers planting Bt corn and Bt cotton report using 30-70%
fewer pesticides, and having a 10-30% increase in yield
• Safer foods (google: spina bifida babies texas corn)
Methods for reducing the development of
insects resistance to Bt toxins
Integrated pest management systems
•
crop rotation
•
planting of non-Bt refuges (~20% of acreage)
•
use of crops with combinations of Cry genes
•
monitor crops for resistant pests
If resistant pests are discovered
•
release of sterile insects
•
apply specific insect growth regulators, feeding inhibitors
•
apply narrow-spectrum chemical pesticides
Roundup Ready crops
Source:
Monsanto
Control soybeans
Roundup Ready soybeans
Roundup Ready crops are resistant to the herbicide glyphosate, which
enables farmers to kill weeds without affecting the crop plants.
Benefits: • increased productivity (Boulder county farmer +60%)
• no-till farming  90% reduction in soil erosion
Roundup Ready crops
Crops: corn, soybeans, sugar beets, canola, alfalfa
Mode of action of Roundup (glyphosate)
•
glyphosphate inhibits the activity of the plant EPSPS enzyme
needed for the synthesis of aromatic amino acids
•
this enzyme is also found in many bacteria, but not in
humans and animals (glyphosate is non-toxic)
•
Roundup Ready plants contain bacterial EPSPS that is not
inhibited by glyphosate
The Golden Rice Project
Vitamin A-deficiency Affects 250 Million
Preschool-Age Children
Vitamin A deficiency causes
• child blindness (~500,000 cases per year)
• immune deficiency problems (~2 million deaths per year)
Solution to Vitamin Adeficiency problem
Background information:
Beta-carotene, a natural
pigment (carrots, oranges,
leaves), is converted to
vitamin A in our bodies.
Golden Rice Project
Create rice and other crop
plants that produce betacarotene in their seeds
Golden Rice seeds containing beta-carotene, a
precursor of vitamin A
One bowl (3 to 5 oz) of cooked Golden Rice 2 per day can
provide 60% of needed vitamin A for young people.
Poor farmers in Bangladesh, Indonesia, Philippines, India(?) earning
less than $10,000 will be receiving free Golden Rice seeds starting
2014 (funded by Bill and Melinda Gates and other Foundations).
Note: This has been a 22 year-long project!
Greenpeace has been sabotaging Golden Rice studies to prevent its release
August 2012
Due to Greenpeace’s obstruction tactics, release of the life-saving
Golden Rice seeds to farmers has been greatly delayed leading to 8
million unnecessary deaths (Patrick Moore, Founder of Greenpeace).
Summary: Some benefits of GE crops
• Better insect pest control -> reduced chemical insecticide
applications and greater yield
• Drought tolerance -> greater yield with less water
• Facilitates no-till farming for soil and water conservation.
• Effective viral, bacterial and fungal disease control
• Improved nutritional properties (Golden rice)
• Better weed control -> greater yield
• Safer foods (e.g. spina bifida babies)
• Greater profitability, shared throughout the agricultural
system (farmers and consumers)
Golden Rice – development time and costs
PP
IPP
PP
DMAPP
PP
GGPP
Phytoene
Phytofluene
-Carotene
Neurosporene
It took a total of 9 years of
basic research and
engineering in the
complementing teams of
Ingo Potrykus and Peter
Beyer and $ 2.4 million to
establish the biochemical
pathway.
It took, however, additional
13 years and $ 22 million to
develop a GMO-product
and pass it through
regulation.
Lycopene
B-carotene is produced in leaves and stems. In seeds the first enzyme is
missing. In Golden Rice the missing enzyme has been replaced.
Some concerns with GM crops
Ethical: Is GE technology playing God?
Economic:
• cross pollination introduces GE material into organic food
products
• concentration of seed business in the hands of a few companies
is risky
Food safety:
• do GE foods have adverse health effects?
• will GE foods provoke allergic reactions?
Environmental:
• development of Bt resistant insects and RR resistant weeds
• transfer of transgenes to relatives of crops
Effects of ratio of organic to conventional agriculture
on pest levels
by Adl et al. Sci. Total Envir. 409-2192-2197, 2011
Organic agriculture benefits greatly from the low levels of pests
maintained by the use of GM crops and pesticides by
conventional farmers.
Above a threshold level of organic to conventional farms the
pest population in organic plots grows rapidly causing epidemics
of pest outbreaks, a major reduction in organic farm output and
in food security.
Conclusion:
Too many organic farms are bad for organic farming!
Examples of GM crops soon to be released
•
•
•
drought resistant corn (several companies) – now released
golden rice (Int. Rice Institute, Philippines) – now released
blight resistant peanut (Virginia Tech)
•
•
•
•
non-browning apple (Okanagan Speciality Fruits)
higher yielding soybean (Monsanto)
cold tolerant eucalyptus (Arbor Gene)
new herbicide resistant crops (Bayer, BASF, Dow, DuPont,
Monsanto, Syngenta)
By 2015 – 120 GM crops worldwide (50% will be crops
developed for local use in Asia and Latin America)
Assessment of health impacts of GM diets using
feeding trials
by Chelsea et al. Food Chem Toxicol. 50:1134-1148, 2012
Review of 12 long-term studies of 90 days to 2 years, and
of 12 multigenerational studies (2-5 generations).
Animal types: mice, rats, cows, pigs, sheep, goats, hens, salmon.
High degree of compliance with European Union guidelines.
Conclusion: GM plants/foods are nutritionally equivalent
to their non-GM counterparts and can be safely used for
food and feed.
Challenges associated with the design and execution of
studies of GM food safety
European Union has developed strict guidelines for studies
Obtaining equivalent GM and non-GM foods is critical
• plants are masters of adaption to local growth conditions
(a plant has to be able to survive and reproduce wherever it germinates)
• good-bad wine vintages (precipitation and temperature affect
composition)
• local growth conditions affect composition: isoflavone (hormonelike compounds) levels of soybeans grown in different parts of Illinois
varied from 47mg/10g to 171mg/10g in same year
• natural toxin (aflatoxin, fumonisin) levels fluctuate
• feeding studies should use “isolines” grown in same place at same
time – complete chemical analysis needed
Challenges associated with the design and execution
of studies of GM food safety (continued)
Experimental design questions
• animal species? animal age? animal sex?
• animals need a balanced diet; what is an appropriate
amount of experimental food in diet (alfalfa, corn, potatoes,
papaya)?
• diets should include multiple concentrations of experimental
food -> concentration-dependent response
• duration of study?
• which health parameters should be tested?