Lecture 24 Controversial
transgenic plants:
risks revisited
Chapter 15
Neal Stewart
Discussion questions
• Discuss controversies in the light of science
and risks of transgenic plants—examples.
• What is the recipe for producing a
• What are the 3 eras in plant biotechnology
controversy? What happened to usher each
in and out?
• How can we critically examine risks and
Mae-Wan Ho
“Genetic engineering biotechnology is inherently
hazardous… which will spell the
end of humanity as we know it,
and of the world at large.”
Genetic Engineering: Dream or Nightmare 1999 p. 1
NGOs and GMOs
The Frankenstein paradigm:
man controls (perverts) nature
with science. Frankenfood
The case of Arpad Pusztai’s
transgenic potatoes
• Insecticidal potatoes expressing a snowdrop
lectin gene (codes for a sugar binding gene)
• Not commercial product
• Feeding study with rats—examined gut features
• Compared transgenic and non-transgenic
• Experimental design and controls?
• Conclusion was that the transformation process
itself or the promoter was responsible for the
Pusztai’s potatoes
Series of events
• Small laboratory study promoted on
national TV (in UK) by the author
• Feeding frenzy by:
– Popular media
– NGOs
• Scientific paper published in the Lancet
(1999) 354: 1353-54.
• Scientific resolution
The case of the monarch and
Bt cry1Ab corn pollen
Monarch butterfly
Series of events
• Small laboratory study published in
prestigious journal (Nature 399: 214)—a
seemingly profound result.
• Prestigious university (Cornell) makes press
• Feeding frenzy by:
– Popular media
– NGOs
• Increased scrutiny by:
– Scientists
– Regulators
• Scientific resolution
Monarch butterfly
What’s riskier?
In October 2001 PNAS– 6 papers delineated the risk for monarchs.
Exposure assumptions made by Losey et al. were not relevant--far off.
Tiered approach—mainly nontargets
What happens when these
levels are used for risk
Wilkinson et al. 2003 Trends Plant Sci 8: 208
Illicit gene
flow from,
GM corn to
corn 2001
Corn belt
The case of Quist and Chapela
Oaxaca, Mexico
Stewart (2004) Genetically Modified Planet
Transgenes from commercial corn to Mexican
landrace corn
Quist and Chapela 2001. Nature 414: 541-543.
• CMV (sic) [CaMV] promoter
DNA putatively found in maize
landraces in Oaxaca, Mexico.
• Claimed transgene
introgression into landraces.
• Used PCR (only) to make
• Study was thoroughly criticized
by scientific community.
• Paper “retracted*” in April
*When a paper is really retracted, the authors’ acknowledge flawed science and officially
retract the paper—it is as if it never existed. In this case, that did not happen. In 2002 the
editor (for the first and only time when he essentially said he wish it would’ve never been
What is introgression?
• Gene flow
• Hybridization
• Introgressive hybridization Edgar Anderson
“The permanent incorporation of genes from one
set of differentiated populations (species,
subspecies, races and so on) into another.”
Stewart et al. (2003) Nature Reviews Genetics
4: 806
Stewart et al. (2003) Nature Reviews Genetics 4: 806
How many plant species introgress
Plant species that
hybridize: 10,000s
Plant species that
introgress: 100s? (165 proposed,
53 documented*)
All plant species
*From Rieseberg and Wendel 1993
Hybrid Zones and Evolutionary Processes
Pp70-109 (Ed., Harrison)
Weak PCR signals =
A few transgenic kernels
Even if results were valid,
Introgression was not
demonstrated. Better
explanation would be spurious
They should have looked at
inheritance and done Southerns
And…Oriz-Garcia et al 2005
PNAS 102: 12238
No transgenic DNA was found in
153,746 Mexican landrace samples.
Landrace maize saga continues
• Piñeyro-Nelson, A. et al. Molecular Ecology 18: 750-761
Found evidence of 35S promoter in 2001 and 2004, but not 2002.
Frequency of 35S in landrace maize= 1.1% by PCR and 0.89%
using Southern blot analysis (but few samples were assayed
using Southerns
• Schoel, B. & Fagan, Mol. Ecol. 18, 4143-4144 (2009).
Genetic ID: claimed that there was “insufficient evidence” for
transgenes in landraces. Argued that qPCR should be the
• Piñeyro-Nelson, A. et al. Mol. Ecol. 18, 4145-4150
– Counter-argued against Genetic ID.
Who/what is Genetic ID?
• “Global leader in GMO detection”
according to the company website
assessed April 13 2010.
• Detection of transgenes using PCR and
real-time PCR.
• In Fairfield, Iowa. Also in Japan and
• Founded by John Fagan (Maharishi
University) in 1996.
Transgenic landrace maize
Series of events
• Quist and Chapela publish Nature paper
• Much criticism by science community
• Nature editor says paper should never have been published
• Ortiz-Garcia et al PNAS paper—no transgenic DNA is found
• Piñeyro-Nelson, et al. Molecular Ecology paper claims
transgenes come and go
• Genetic ID claims authors misinterpret data
• Probably low level of transgene presence?
• Decision is made to allow field trials in Mexico of transgenic
The Rural Advancement Foundation
International (now the ETC Group) renamed
TPS or GURTs to
Words are powerful!
The case of “Terminator” technology
AKA Technology Protection System
AKA Gene Use Restriction Technology
US Patent 5,723,765; Inventors: Melvin Oliver, et al. issued March 3, 1998—
licensed to Delta and Pineland
Control of plant gene expression
A method for making a genetically modified plant comprising regenerating a
whole plant from a plant cell that has been transfected with DNA sequences
comprising a first gene whose expression results in an altered plant phenotype
linked to a transiently active promoter, the gene and promoter being separated
by a blocking sequence flanked on either side by specific excision sequences, a
second gene that encodes a recombinase specific for the specific excision
sequences linked to a repressible promoter, and a third gene that encodes the
repressor specific for the repressible promoter. Also a method for making a
genetically modified hybrid plant by hybridizing a first plant regenerated from a
plant cell that has been transfected with DNA sequences comprising a first gene
whose expression results in an altered plant phenotype linked to a transiently
active promoter, the gene and promoter being separated by a blocking sequence
flanked on either side by specific excision sequences to a second plant
regenerated from a second plant cell that has been transfected with DNA
sequences comprising a second gene that encodes a recombinase specific for
the specific excision sequences linked to a promoter that is active during seed
germination, and growing a hybrid plant from the hybrid seed. Plant cells, plant
tissues, plant seed and whole plants containing the above DNA sequences are
also claimed.
Evolution of GMO controversies
• Until 1998: few controversies
• 1998-2001: “Golden age” of controversies—
characterized by NGO and media frenzies.
Scientists were passive.
• 2002 until now: Fewer controversies. Why?
– Over 1 billion acres and 100 trillion transgenic
plants—no one has died.
– Wary media
– Proactive scientists (see response to Quist and
Seralini rat tumor study
• Rats were fed Roundup ready corn or
conventional corn over the rat’s lifetime (2 years)
(Food and Chemical Toxicology 50:4221; 2012).
• Higher incidence
of cancer and death
• Conclusion: the GMO
corn or Roundup is
Scientific response to Seralini
• Study criticized on the basis of experimental
design (low sample size) and use of SpragueDawley rats (susceptible to cancer).
• European Food Safety Authority concluded the
study was of “insufficient scientific quality for
safety assessments.”
• Raised questions of scientific misconduct since
the researchers will not release their data.
• Paper was retracted by the journal in 2013.
• No technology is risk-free, but plant
biotechnology is not risky per se
• Food, corporate control, and environment
causes are social issues that reach
beyond science
• GMOs are one tool for agricultural and
environmental security and sustainability
Historical global area and value of
transgenic crops
Marshall, A. 2012. Nature Biotechnology 30:207
Global area of transgenic crops by country
Marshall, A. 2012. Nature Biotechnology 30:207
Big environmental benefits
of today’s transgenic crops
Herbicide tolerant crops have increased and
encouraged no-till agriculture– less soil erosion.
Over 1 million gallons of unsprayed insecticide
per year.
• Weighed against benefits
• Weighed against risks of competing
practices and technologies (none are riskfree)
• Weighed against not adopting
Controversies result from oversimplifications
coupled with a desire to inflame.

Molecular genetics of gene expression