“If you desire peace,
cultivate justice, but at
the same time cultivate
the fields to produce
more bread; otherwise
there will be no peace.”
Norman Borlaug
(Nobel Peace Prize 1970)
GM Crops and Sustainable Food
Systems
Part I: Molecular Biology, Organic Farming, Agrobacteriumbased transformation methods and crops
L. Andrew Staehelin
Department of Molecular, Cellular and Developmental Biology
University of Colorado, Boulder
ENVS 3525, Sustainable Food Systems, CU class
October 13 & 15, 2015
What makes a great scientist (and cartoonist)?
“To see what other people can see and think what
nobody else has thought”
Albert Szent-Györgi
Nobel Laureate 1937
QUESTION: What does this graph demonstrate?
GM Food Hysteria
Author: Mary Shelley
Written 1816 – “The year
without a summer” and
world-wide famines due to
Mount Tambora volcano
explosion in 1815 (100x
bigger than Mt. St. Helens)
Writing contest with Percy
Shelley, Lord Byron and John
Polidori: who could write the
best horror story during
vacation on lake Geneva
(June). Story about scientist
who created life and was
horrified by outcome.
Frankenstein food name origin
1992:
Reporter from London’s Daily Telegraph
writing about the first GMO Flavr Savr
tomato, which does not require
refrigeration for storage, called it “the
cudliest of Frankenfoods” (a mysterious
and scary invention)
The big problem – how can we feed the world?
my birth
Industrial revolution
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.
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)
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.
“Central Dogma” of molecular biology
(simplified)
DNA  RNA  PROTEIN
DNA: deoxyribonucleic acid
RNA: ribonucleic acid
GMO: Genetically Modified Organism
GM crop: Genetically Modified Crop
GM Food: Genetically Modified Food
QUESTION:
What does “genetically modified” mean?
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.
There is also not enough cow manure to fertilize fields – think cornfields in Kansas.
• Conclusion: organic farming does not provide an option for feeding
the world now or in the future.
• Best solution: combine the best features of organic farming with
the best features of modern agriculture, including GM crops.
This is already being done by traditional farmers who believe in sustainability!
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, wind and salinity stresses
• increase productivity of plants (more seeds, bigger fruit)
• improve nutrient value (increased content of desired products,
e.g. protein to replace 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, but still important
•
time consuming (~10 years) due to long generation times
Mutagenesis – radiation, chemical, tissue culture growth
•
results unpredictable (long cleanup of unwanted mutations)
Genetic engineering
• can transfer genes of any organism (cis-genic, trans-genic)
• can suppress the expression of existing genes (silencing)
• can precisely and quickly modify any plant gene to change its
properties
Original Method of Plant Genetic Engineering
Lateral gene transfer, the mechanism of DNA transfer
exploited by Agrobacterium, is natural, predates sex,
and is still used by billions of organisms every day
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 vir
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 vir genes coding for opin synthesis enzymes
•
removal of vir 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
GM Crops and Sustainable Food
Systems
Part II: Bt- and Roundup Crops, RNAi and CRISPR-Cas9
transformation methods, Golden Rice, Sustainable food
systems, and anti-GMO claims versus scientific facts
L. Andrew Staehelin
Department of Molecular, Cellular and Developmental Biology
University of Colorado, Boulder
ENVS 3525, Sustainable Food Systems, CU class
October 13 & 15, 2015
Proof of Global Warming
Bt crops – Cry protein producing 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 (every cell produces Cry proteins)
• Farmers planting Bt corn and Bt cotton report using 30-70%
fewer insecticides, and having a 10-30% increase in yield
• Safer foods (google: spina bifida babies texas corn)
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 holes in corn kernels allow Fusarium
molds to infect plants: 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.
Roundup Ready (glyphosate-resistant) crops
Crops: corn, soybeans, sugar beets, canola, alfalfa
Mode of action of the herbicide 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
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 +30%)
• no-till farming  90% reduction in soil erosion
Problem: Overuse! Every farmer wants to reap the benefits.
Drought tolerant transgenic wheat being developed
Source:
CIMMYT
Drought tolerant wheat plants (left) and control plants
(right) after 10 days without water. The drought tolerant
plants contain gene from Arabidopsis.
Drought tolerant corn is already being sold (20% less water).
What criteria should be used to define a
GM plant/food?
CLAIM: Transfer of genes between unrelated organisms is “unnatural”
Conclusion:
All sweet potatoes we
eat, including certified
organic, are GMOs!
Proc. Nat. Acad. Sci. USA 112:
5844-5849, 2015
RNAi technique used for protecting crops against pathogens
RNA from pathogen
Small interfering RNA
with pathogen recognition
code
Enzyme complex that binds
to single RNA strand and can
cut recognized DNA
Recognition and cutting of
pathogen mRNA -> no
protein
Papaya trees protected by RNAi against ringspot virus
Diseased, non-transformed trees in foreground, and healthy, transgenic trees behind.
Developed by Hawaiian scientists in 1996. About 99% of Hawaiian papaya are GMOs!
Successful applications of RNAi in crop breeding
(RNAi is also used naturally by plants to protect themselves)
• Ringspot virus-resistant papaya (Hawaii)
• Virus-resistant beans (Brazil)
• Virus-resistant crop cassava (Africa)
• Fungal-resistant bananas
• Nematode-resistant soybeans
• Reduced gluten wheat
• high oleic acid soybean oil
CRISPR-Cas9 method for editing (precisely modifying) DNA
(requires knowledge of DNA sequence of gene)
Synthetic RNA with
specific DNA recognition
site
Enzyme that holds RNA
& DNA together, cleaves
Plant DNA
Cut plant DNA
Modified plant DNA
The Golden Rice Project
Designed to reduce vitamin A-deficiency in diets of poor people in developing
countries (~250 million)
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 receive free Golden Rice seeds when permitted
(funded by Bill and Melinda Gates and other Foundations).
Golden Rice
and the Precautionary Principle
Greenpeace has campaigned against the release of
Golden Rice citing the precautionary principle.
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).
Is this proper use of the precautionary principle by
Greenpeace?
Why do the Organic Food Industry and Greenpeace
continue to agitate against GM crops and foods?
MONEY!
The $50 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.
Sustainable Food production
• A sustainable food system is a system that delivers food security
for future generations.
• A sustainable food system must maintain current levels of
agricultural productivity and provide a pathway for increasing
food production in the future, while reducing the use of nonrenewable resources.
• Sustainable food production systems must be based on the use
of all available farming resources (including GM crops) suitable
for a given environment.
• Sustainable food systems must conserve soil, water and mineral
resources, while respecting biodiversity and natural ecosystems.
• Sustainable food systems must allow for improvements in the
nutritional qualities of foods and enable the substitution of meat
products with plant products.
Why are GM Foods/Crops controversial?
The following are
claims made by anti-GMO activists
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
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)
How many GM food and environmental safety
studies have been published?
Between 2002 and October 2012
scientists 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. Examples: Pusztai and Seralini studies
CLAIM: GMO foods are unsafe, have adverse health effects
CLAIM: Roundup Ready crops produce “superweeds”
Definitions of a weed by weed scientists:
• A weed is a plant undesirable in a particular situation (e.g. in a
field)
• A vigorously growing plant that is not valued where it is
growing and choking more desirable plants
What is a “superweed?”
This is NOT a term used by weed scientists.
A term coined by anti-GMO activists for herbicide-resistant
weeds and designed to scare the public
QUESTION: Are “superweeds” a problem for organic farmers?
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!
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)
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
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