Transcript Transgenic - SAI

Genetically Modified Crops
Miracle Crops or Frankenfoods?
Thomas L Sims, Ph.D.
Department of Biological Sciences & Plant Molecular
Biology Center, Northern Illinois University
Summer Ag Institute: DeKalb County Farm Bureau, June 17, 2014
My Background
• Mother’s family were dairy farmers in Wisconsin
• B.S. University of Wisconsin, Ph.D. University of
Oregon, Post-doctoral research fellow at UCLA
• While at UCLA, part of a team that was the first group
in the U.S. to make “transgenic” (GMO) plants, by
putting a gene from soybean into tobacco
• Came to NIU in 1992. Current research on Plant
reproduction & Petunia Genome Project
+
Petunia integrifolia
Petunia axillaris
Petunia hybrida
Challenges
• Human population growth
• Increased economic prosperity in developing
countries
• Loss of arable land & urbanization
• Global climate change
• How do we feed a larger population, on less
land, with fewer inputs, while facing the
challenges of reductions in yield because of
climate change?
Knowledge-Based Approaches
• Molecular Genetics
• Plant genomic sequencing (rice, corn, soybean,
tomato, pepper, tobacco, petunia, Arabidopsis thaliana)
• Plant Biochemistry, Plant Physiology
Limitations
• Over 250,000 species of flowering plants, but all of
agriculture is based on ~30 species and just a few of
these provide the vast majority of calories
GMO
• Genetically-modified organism
– Genetically-modified crops
– Genetically-modified food
•
•
•
•
•
What are GMOs?
How do you make them?
Why make them?
Are there legitimate concerns about GMOs?
What’s in the future?
Genetic Modification
• Ruby-Red Grapefruit (ionizing
radiation)
• Golden Raisins/Sultanas
(processing mutant)
• Seedless fruits (ionizing
radiation)
• Cultivated tomato (mutations in
HT-B, S-RNase, uniformripening)
• Cultivated potato (tetraploid)
• Modern (non-transgenic) rice
• Modern maize (from teosinte)
Transgenic Plants
• DNA encodes genetic information
• Can physically isolate and clone DNA
sequences encoding specific genes
• Transgenic organisms are those where:
– A NEW gene has been inserted and is expressed
or
– An EXISTING gene has been turned off
• Insert cloned genes into plant cells and regenerate whole transgenic plants
• Transgenic plants = GMO plants
Agrobacterium tumefaciens, a natural soil
bacterium, causes crown galls
Plant Regeneration from Tissue Culture
Fertile plants can be regenerated from single cells
Just replace the T-DNA in Agrobacterium
with gene of interest, let the bacterium
transfer the gene to the plant & regenerate
Expressing “Transgenes”
• Source of expressed gene of interest can be
anything:
– A gene from a different plant (Golden Rice)
– A gene from a bacterium (Bt-corn, Round-Up
Ready Soybeans)
– A gene from an animal (drug production)
– A gene-construct that turns-off a gene target
(Flavr-Savr, Arctic apple)
• Must have plant-specific “switch” or promoter
RNA interference (RNAi)
Inhibition of Gene
Expression by RNA
degradation,
translational inhibition
or chromatin
modification
Present in all higher
eukaryotic organisms.
• Much of human
genome is regulatory
miRNA genes
• Anti-virus defense
mechanism in plants
• Based on sequence
complementarity to target
mRNA
Types of Transgenic Modifications in GMOs
• Transfer of bacterial protein-coding
gene (HT, Bt, Golden Rice, droughttolerant corn, cold-tolerant Eucalyptus)
• Transfer of non-coding viral gene (GM
Papaya in Hawaii)
• Transfer of a gene from a different
plant species (Golden Rice, GreenBlight tolerant oranges, yield-enhanced
soybean)
• Down-regulation of endogenous plant
gene (Arctic apples, InnateTM
potatoes, reduced CN Cassava)
• Down-regulation of insect-pest gene
(Corn rootworm III)
GMO Regulation in United States
• USDA-APHIS
– Regulates “environmental risk”
– In practice, regulates all GMO products
• EPA
– Regulates any GMO product involving a pesticide (e.g.
herbicide-tolerance, Bt corn/cotton)
• FDA
– Regulates Food and Feed Safety
– Potential allergens? New toxic substances? Altered
Nutritional Composition?
GMO Regulation in Europe
• European Food Safety Authority
• Scientific Panel, founded 2002
•Broad-based European authority for food safety
• GMO Panel
• Has approved every GMO application it has reviewed
• Recommendations go to EC Standing Committee on
Food Chain and Animal Health
Luxembourg & Austria 100% “No” to approval
Sweden, Finland, Czech, Netherlands, 100% “Yes”
• EFSA also rejected ‘health-claim’ benefits of food
additives and other foods
Some Brief Examples
• Flavr-Savr tomato (first transgenic, 1994)
• Bt-corn (insect resistance)
• ArcticTM apple (non-browning, scheduled for
release soon)
• Golden Rice
Flavr-Savr Tomato (1994)
• Conventional tomatoes have a
mutation in uniform ripening that also
reduces flavor
• Conventional tomatoes harvested
green, stored, exposed to ethylene gas
• Flavr-Savr tomato engineered to turnoff “polygalacturonase” (PG) gene
involved in rotting
• Leave on the vine to ripen, then pick
• Better taste, flavor & color
• Marketed in DeKalb but no longer in
production
Bt Corn
Bt Cotton
• Genetic engineering for resistance to
European Corn borer or related pests
• Conventional chemical sprays don’t
work on corn borer
• Huge amounts of chemical sprays
used on cotton
• Genetic engineering of ‘crystal-toxin’
(Cry) gene from Bacillus thuringiensis
•Solution of Bt bacterium
sold off the shelf as
insecticide for organic
gardening
• Non-toxic to humans &
animals
• Non-toxic to non-target
insects
Bt protein Mode of Action
Only in
specific
insects. Not in
animals or
other insects.
Adoption of Bt cotton has resulted in large
decrease in use of chemical insecticides
National Research Council Report 2011, on the Environmental
Effects of Transgenic Crops
Enzymatic Browning
(Polyphenol oxidase)
apples
Potatoes
RNAi: Polyphenol
oxidase (PPO)
Arctic Apple
• Onkanagon Specialty Fruits, British Columbia, CA
• Non-browning apple
• RNAi of four members of polyphenol oxidase gene
family
• In last phases of regulatory process for unregulated
release in U.S. and Canada
• www.arcticapples.com
Intention of the
company is to
label the
individual apples
as GMO, once
they are approved
for release
“Natural” PPO Mutant
• 1962: “Bruce’s Sport” mutation of
Sultana grape variety. Lacked PPO.
• Used to produce “Golden Raisins”
Completely unregulated process
• Mutation deciphered 1992
PPO protein precursor, 67 kDa protein
10.6 kDa transit peptide
40.2 kDa active enzyme
16.2 kDa C-terminal peptide
• In “Bruce’s Sport”, mutation eliminates cleavage of
C-terminal peptide
• “New” protein of 60 kDa without PPO activity
Peter Beyer, Freiburg
Ingo Potrykus, Zurich
Vitamin A deficiency
• Important for vision
• Important for immune system
• -carotene (provitamin-A) cleaved to
Vitamin A
• 400 million people at risk, 100-140 million
children
• 250,000 - 500,000 cases of blindness. 50%
of these die within one year
Global Vitamin-A Deficiency Patterns
Vitamin-A deficiency largely due to poor diet, subsidence diet,
especially of rice (Asia) or Cassava (Africa) which lack Vitamin-A
Steps shown in GREEN are present in rice, others are not
Gene construct for Golden-Rice-2
Glu= Rice glutelin promoter (endosperm specific)
tpSSU = transit peptide Rubisco small-subunit (pea)
CrtI = Bacterial desaturase CRTI
Nos = nopaline synthase terminator
Psy = Phyotene synthase (daffodil)
Ubi1= maze polyubiquitin promoter
Pmi = Phosphomannose isomerase (E. coli)
Long Road in
Development to
Public Release
Potrykus “Regulation must be
revolutionized” Nature 466: 561
(2010)
2014?
Future Developments?
• Marker-free & vector-free GMOs (e.g.
InnateTM potatoes, uses only modified potato
DNA)
• Reduction of antinutritional compounds
(reduced CN/enhanced Fe Cassava)
• Improved Nitrogen utilization (less fertilizer
input)
• Golden Rice II release?
Resistance to GMOs
• Organized and effective political opposition
– Fears/concerns about corporate control of food (March
Against Monsanto)
– Safety concerns, Environmental concerns
– Philosophical concerns
• How legitimate are the issues raised?
– Some problems do exist, but these can (and will) be
addressed because of an understanding of the underlying
scientific cause
– Many are blown out of proportion, either deliberately or
because of a lack of understanding
Example: herbicide resistant weeds
• Fears/accusations of GMO “superweeds”
• Requirements for genetic transfer of resistance
–
–
–
–
Sexually-compatible weedy relative in geographic proximity
Overlap in flowering time
Pollinator
Positive Selection
• Canola, sugar beet most problematic
• Soybean, corn less so
• Real problem is not cross-pollination but
conventional natural-selection & population genetics
Evolution of weeds resistant to Glyphosate
All of these are due to natural selection on existing weeds, not pollen transfer
Also: use of glyphosate has increased total amount or herbicide used (lbs/acre)
BUT glyphosate is far LESS toxic than previous herbicides, so its use is a
environmental plus compared to prior practice
Addressing Herbicide Resistance
• No “super” weeds; still susceptible to other herbicides
• “Stacking” two or more resistance genes (glyphosate,
glufosinate, dicamba, 2,4-D) will greatly slow or
eliminate development of resistance because
resistance required simultaneous mutations in two
different genes
• More attention to crop rotation (don’t use the same
trait in all crops, all the time)
Anti-GMO
Headline
‘Agent Orange’ Crops
Would Trigger Massive
Increase in Use of Toxic
Pesticide 2,4-D (Jan 2014)
• Misleading: 2,4-D (synthetic plant hormone) was one ingredient
of “Agent-Orange”, but NOT the dangerous one (2,4,5-T, whose
synthesis produced dioxin as a by-product. Dioxin was the real
culprit)
• 2,4,5-T is no longer manufactured or used
• 2,4-D is in >1500 herbicides and has been used since the 1940’s
GMO Labeling
•
•
•
•
•
•
Passed in Vermont, Connecticut
Defeated in Washington, California
Under consideration elsewhere, including Illinois
How food is produced versus what it contains
USDA doctrine of “Substantial equivalence”
Inconsistencies: (crops sprayed with Bt bacteria,
expressing the Bt protein, would not have to be
labeled, but those expressing transgenic Bt protein
would have to be labeled)
Two web sites with objective information
http://www.geneticliteracyproject.org/
Stronger life, stronger science, and stronger
communication.
http://www.biofortified.org/
Questions?
GRII in cultivation