9-Misc: U.S. scientists having problems with the term "GMO"

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TITLE:  The Difficulties of Defining the Term "GM"
SOURCE: Science 303 (5665): 1765-1769, by P. Grun, T. Ramsay & N. Fedoroff
        http://www.sciencemag.org:80/cgi/content/full/303/5665/1765b
DATE:   Mar 19, 2004

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The Difficulties of Defining the Term "GM"
P. Grun

I am writing to urge the maintenance of the commonly understood meaning
of the acronym "GM" and in opposition to a changed use that appeared
prominently in a recent Perspective by N. V. Federoff ("Prehistoric GM
corn," 14 Nov., p. 1158). Through much of the history of genetics,
genetic modification was attained only by the classical methods involving
crossing, backcrossing, selfing, and so forth, and there was a definite
limitation imposed by the relationships among organisms involved or the
source of genes that could be combined and recombined. After DNA transfer
via Agrobacterium and gene guns was developed, that limitation
disappeared, the processes of genetic manipulation became much more wide-
ranging, and very different problems associated with the new
methodologies surfaced. The expression "genetically modified organism,"
"GMO," or, more commonly, "GM," was coined for these methods. An
extensive literature has been built up with a common understanding that
associates the term "GM" with genetic engineering. The result has been
the evolution of an acronym having a meaning different from the words it
symbolizes, for GM is only a small part of the total literature on
genetic modification. Major economic implications are tied up with the
term, whose recognition may well influence whether GM crops become common
in commerce. My point is that the distinctions between classical genetic
modification and its acronym are clearly understood.

Fedoroff's Perspective breaks with that usage, even in its title, and so
removes the distinction. I do not wish to concentrate on this paper, for
there may well be others that use the terms as synonyms, but I do object
to the practice. It is not a question of whether genetic engineering is
good, bad, or irrelevant, but clarity of understanding requires that a
distinction be recognized. If breaking with the identification of GM with
genetic engineering becomes common, the distinction will disappear and
any genetic modification will be considered a GM. Such a redefinition
would confuse readers and complicate the already complex discussions on
this topic. Let's keep communication clear in this controversial field
and restrict the term "GM" to its engineering roots.

Paul Grun
Department of Horticulture, Pennsylvania State University, 103 Tyson
Building, University Park, PA, 16802, USA.
E-mail: pxg3@psu.edu

*****

N. V. Fedoroff's Perspective "Prehistoric GM corn" (14 Nov., p. 1158)
seems calculated to obscure important issues in the debate over the
safety of genetically modified organisms (GMOs). In any meaningful
discourse concerning GMOs, distinctions must be made between the
different techniques, ranging from traditional selective breeding to
biotechnology based on recombinant DNA, used to incorporate new genetic
material into existing organisms.

In her Perspective, Fedoroff resorts to two deceptive rhetorical devices
to obscure the distinction between bioengineering and selective breeding:
She defines the term "genetic modification" in such a way as to include
prehistoric crop domestication, and she uses the words "fast" and "rapid"
in two different time scales. Fedoroff reports that maize probably
originated in southern Mexico about 9000 years ago, describes how
selective breeding had yielded corn with a modern genetic profile by
about 4400 years ago, and cites findings of maize cultivation in the
southwestern United States more than 3000 years ago as evidence that
"[t]he GM corn spread far--and fast." Two paragraphs later, she concludes
that "the apparent loss of genetic diversity following the introduction
of high-yielding Green Revolution wheat and rice varieties in the 1960s
and 1970s, and attending the rapid adoption of GM crops today, is far
from a new phenomenon."

In a talk given for the Penn State Lectures on the Frontiers of Science,
Fedoroff defined a genetically modified organism as one that "was
modified using contemporary molecular techniques" ( 1). By this
definition, the maize grown by pre-Columbian indigenous peoples does not
qualify as a GMO. Contemporary bioengineering techniques create new crops
markedly faster than traditional breeding can, and the genetic
modifications induced tend to be qualitatively different. Furthermore,
the speed with which modern marketing and distribution channels
disseminate GMOs is very different from the gradual spread of
domesticated crops ( 2). Fedoroff's implication that this unprecedented
speed of creation and dissemination is "far from a new phenomenon" is, at
best, misleading.

Tim Ramsay
McLaughlin Centre for Population Health Risk Assessment, University of
Ottawa, 1 Stewart Street, Ottawa, ON K1N 6N5, Canada.

References
PowerPoint presentation, available at
www.science.psu.edu/alert/frontiers/Fedoroff3-HTML/index.htm
(2001).
P. Gepts, Crop Sci. 42 , 1780 (2002).

*****


Response

My words were chosen with care. It is indeed true, as Ramsay points out,
that the contemporary definition of genetically modified, or GM, applies
only to plants modified by molecular techniques and that I have used this
definition both in writing and in public lectures. But it is becoming
increasingly clear that the distinction is not just artificial and
unhelpful, but profoundly counterproductive on a global scale.

Both Grun and Ramsay maintain that meaningful discourse requires making a
distinction between "traditional selective breeding" and "biotechnology
based on recombinant DNA." I disagree. It is precisely this distinction
that has created the widely accepted, albeit mythical, view that
"traditional" plant breeding is somehow gradual, and, yes, natural,
whereas contemporary techniques are rapid and unnatural.

According to the Mutant Variety Database, established by the
International Atomic Energy Agency and the Food and Agriculture
Organization of the United Nations ( 1), more than 2000 crop varieties
grown today were created using chemical or radiation mutagenesis. Is
using neutron radiation to create the popular Rio Red grapefruit variety
gradual and natural? Is using the somaclonal variation arising as a
result of passage through tissue culture to create mutant herbicide-
tolerant Clearfield Corn less rapid and unnatural than introducing
bacterial or mutant genes cloned by molecular techniques to create Round-
up Ready corn and soybeans?

Pinstrup-Andersen and Schioler ask, "Why, in the debate on natural versus
unnatural, should we draw the line right here, right now, at the point
where genetic engineering has entered the scene?" [( 2), p. 80-81]. And
it is indeed a puzzle that people blithely accept churning up genomes
with radiation, mutagenic chemicals, and a variety of other techniques,
including intergeneric crosses, while looking askance at the newer, very
much less disruptive molecular methods. But maybe they don't know what
traditional breeders do.

Moreover, the ability to move genes between species is not a recent, or
even a human invention. Agrobacterium and its plant-transforming plasmids
are natural: Quite without human intervention, these bacteria developed a
set of plant genes useful to the bacterium, as well as the ability to
transfer them to plant cells without killing the plant. Why is using this
natural genetic engineering system to introduce genes coding for
bacterial Bt proteins to protect plants from insect attack less natural
than spraying fields with concentrated preparations of the Bt bacteria
grown in huge fermenters and sold in stores? If you have followed the
monarch butterfly flap, you will know that the consensus of a very large
U.S.-Canadian project to assess the impact of GM corn on the monarch came
to the conclusion that only about 3 in 10,000 larvae will be in danger of
getting sick or dying from eating corn pollen expressing Bt genes ( 3).
This seems as benign and sensible an approach to crop protection as
replacing a drug with a vaccine is in human health care.

It is time to eliminate the altogether artificial boundary between what
humans did before molecular techniques were developed and what they do
now to improve their crop plants--a point I sought to make in my
Perspective. A mutation is a mutation, whether spontaneous, induced by
tissue culture, or induced by radiation mutagenesis. The kinds of genetic
changes that underlie the origin of corn from teosinte are not
fundamentally different from those that gave us dwarf Green Revolution
rice, seedless oranges, or Rio Red grapefruit. And if they spread more
slowly than they might today, it was probably only because people hadn't
yet invented trucks, trains, and planes.

What's new is that our growing understanding and knowledge of genes and
how they function means that we don't have to wait for just the right
spontaneous mutation to show up, nor do we have to hurry the process by
bashing genomes randomly with radiation. We can instead identify and
isolate just one target gene and alter it by molecular methods in a very
precise way. We can then introduce it into a plant with minimal genomic
disturbance.

I agree with Grun's assertion that the use of the term "GM" has economic
implications and may influence whether GM crops are or are not accepted.
In 2002, Zambia's president Mwanawasa puzzled people around the world by
rejecting a much-needed shipment of U.S. corn for his starving nation,
despite assurances by the United States, the United Nations, and NGOs
that the GM corn was safe to eat and was, indeed, the same as that eaten
daily in the United States, Canada, and other countries. But he was
neither ignorant nor nuts. Along with the rest of Africa, Mwanawasa was
confronted with a truly Hobbesian choice: starve now or lose access to
European GM-free markets in the future. As Mexico has discovered, seeds
from food aid shipments find their way into farmers' fields.

It seems almost beyond comprehending, yet the apparently personal
preferences of European consumers for foods made from plants that have
been genetically modified in many ways, but not by molecular methods, may
set Africa's agricultural and economic agenda. In a recent Op-Ed piece,
Normal Borlaug (who won a Nobel prize in 1970 for developing the Green
Revolution wheat strains) wrote, "Biotechnology absolutely should be part
of Africa's agricultural reform; African leaders would be making a
grievous error if they turn their back on it" ( 4). He strongly urges
Africa not to follow the lead of Europe, where biotechnology has been
"demonized."

But how can Africa afford to adopt GM technology if doing so precludes
future access to European markets? Yet how can Africa afford not to adopt
GM technology, which is scale-independent and biologically based, in its
struggle to attain food security? Are we not part of the problem with our
insistence on hanging a special label on crops genetically modified by
molecular techniques, quite without evidence of any kind that these crops
pose new environmental problems or that foods made from them create new
health risks? As Kenyan plant breeder Judith Wambugu said, " You people
in the developed world are certainly free to debate the merits of
genetically modified foods, but can we please eat first?" ( 5).

Nina Fedoroff
Huck Institutes of the Life Sciences, Pennsylvania State University, 219
Wartik Laboratory, University Park, PA 16802, USA.
E-mail: nvf1@psu.edu

References
1) See www-infocris.iaea.org/MVD/.
2) P. Pinstrup-Andersen, E. Schioler, Seeds of Contention: World Hunger
and the Global Controversy over GM Crops (Johns Hopkins Univ. Press for
the International Food Policy Research Institute, Baltimore, MD, 2000).
3) M. K. Sears et al. ,Proc. Natl. Acad. Sci. U.S.A. 98 , 11937 (2001).
4) N. Borlaug, "The next green revolution," N.Y. Times , 11 July 2003,
section A, p. 17.
5) J. Wambugu, from a 2003 interview with Joe Schwarz of McGill
University. Pdf file is available at
www.oss.mcgill.ca/biotech/africa.pdf


                                  PART II
-------------------------------- GENET-news -------------------------------

TITLE:  Prehistoric GM Corn
SOURCE: Science 302 (5648): 1158-1159, by Nina V. Fedoroff
        http://www.sciencemag.org/cgi/content/full/302/5648/1158
DATE:   Nov 14, 2003

------------------- archive: http://www.genet-info.org/ -------------------


AGRICULTURE: Prehistoric GM Corn

Corn (maize) is arguably man's first, and perhaps his greatest, feat of
genetic engineering. Its huge ears--each packed with firmly attached
kernels filled with starch, protein, and oil--make it a food staple.
Contemporary corn, unlike its wild grassy ancestor teosinte, can't
survive without people because it can't disperse its own seeds. The
origins of maize have long intrigued geneticists, but only recently have
new molecular methods enabled evolutionary sleuths to pinpoint its
origins and identify the genetic modifications (GMs) that enabled the
radical transformation of teosinte into contemporary maize. On page 1206
of this issue, Jaenicke-Després, Doebley, and their colleagues ( 1)
provide the latest chapter in this detective story and suggest that
prehistoric people were quick to adopt GM corn.

Teosinte and corn ( Zea mays ) don't look much alike, but they are
interfertile. Teosinte-corn hybrids arise in the wild but look so
different from either parent that they were originally classified as a
different species ( Zea canina ). In the 1920s, Beadle examined
chromosomes in teosinte-corn hybrids and concluded that the two plants
belonged to the same species, and even shared the same chromosomal order
of genes. That should have resolved the question of corn's origins, but
it didn't.

In 1938, the eminent maize geneticist Mangelsdorf proposed that maize
evolved from an extinct South American maize species and that teosinte
originated from a cross between another grass, Tripsacum , and maize (
2). Although cumbersome, this hypothesis was widely accepted, and
Mangelsdorf and Beadle sparred publicly for years. Upon retirement,
Beadle organized an expedition to Mexico to look for more wild maize
relatives, returning with seeds that proved invaluable to the next
generation of molecular archaeologists. The Tripsacum hypothesis was
briefly resurrected in the mid-1990s, but by then molecular evidence
overwhelmingly favored the notion that teosinte was the ancestor of
modern maize ( 3).

So how, when, and where was teosinte transformed into maize? Beadle gave
his mentor, Emerson, credit for the idea that just a few mutations
changed teosinte into maize ( 4). Analyzing backcrossed maize-teosinte
hybrids with molecular probes, Doebley's group came to a startlingly
similar conclusion: The differences between maize and teosinte could be
traced to just five genomic regions ( 5). In two of these regions, the
differences were attributable to alternative alleles of just one gene:
teosinte glume architecture (tga1 ) and teosinte branched (tb1 ), which
affect kernel structure and plant architecture.

The tga1 gene controls glume hardness, size, and curvature ( 6). Teosinte
kernels are surrounded by a stone-like fruitcase, assuring their
unscathed passage through an animal's digestive tract, which is required
for seed dispersal. But the plant's reproductive success is the
consumer's nutritional failure. Not surprisingly, one of the major
differences between maize and teosinte kernels lies in the structures
(cupule and outer glume) enclosing the kernel. Maize kernels don't
develop a fruitcase because the glume is thinner and shorter and the
cupule is collapsed. The hardness of teosinte kernels comes from silica
deposits in the glume's epidermal cells and from impregnation of glume
cells with the polymer lignin. The maize tga1 allele supports slower
glume growth and less silica deposition and lignification than does the
teosinte tga1 allele.

The tb1 locus is largely responsible for the different architecture of
the two plants. Teosinte produces many long side branches, each topped by
a male flower (tassel), and its female flowers (ears) are produced by
secondary branches growing off the main branches. Modern corn has one
main stalk with a tassel at the top. Its lateral branches are short and
bear its large ears. Much of the difference is attributable to the tb1
gene, originally identified in a teosinte-like maize mutant. Mutations
generally abrogate gene function, indicating that the maize allele acts
by suppressing lateral shoot development, converting grassy teosinte into
slim, single-stalked modern corn and male into female reproductive
structures ( 7).

Knowing that this cluster of traits is controlled by just two genes makes
it less surprising that genetic differences in these genes could render
teosinte a much better food plant. Yet however useful to people, a tga1
mutation would have been detrimental to teosinte, making it more
vulnerable to destruction in the digestive tract of the consumer and so
less able to disperse its seeds. Thus, the only way this mutation could
have persisted is if our ancestors propagated the seeds themselves. This
implies that people were not only harvesting--and likely grinding and
cooking--teosinte seeds before these mutations came along, but also were
selecting for favorable features such as kernel quality and cob size. In
turn, this suggests a "bottleneck" in corn evolution: Several useful GMs
were brought together in a single plant and then the seeds from this
plant were propagated, giving rise to all contemporary maize varieties.
Such a prediction can be tested by calculating the number of generations
and individuals it would take to account for the molecular variability
present in contemporary maize. The results of such a test suggest a
bottleneck for maize domestication of just 10 generations and a founding
population of only 20 individuals ( 8). Did this happen once or many
times? Because genetic differences arise at a fairly constant rate, this
question can be answered by constructing family trees using similar
sequences from different varieties of teosinte and contemporary maize.
The results are unequivocal: All contemporary maize varieties belong to a
single family, pointing to a single domestication event.

Knowing how quickly differences arise, how many there are today, and
where the family of origin survives, it is possible to determine when--
and where--it all started. The answer is that maize most probably arose
from teosinte of the subspecies parviglumis in the Balsas River basin of
southern Mexico roughly 9000 years ago ( 9). Recent redating of cobs from
the Guilá Naquitz cave (about 500 km from the Balsas River basin)
demonstrated that they were more than 6200 years old, providing
archaeological support for the molecular findings ( 10 ,11 ). These
earliest corn cobs don't look much like those of modern corn, but they
look even less like teosinte cobs (see the figure). They are tough and
have several rows of tightly attached kernels, implying that the plants
wouldn't have survived without people to detach and plant the seeds. By
contrast, teosinte's reproductive structure, the rachis, falls apart when
mature to release its hard seeds. Thus, even 6000 years ago, ancient
maize cobs were already corn-like.


The GM corn spread far--and fast. Maize appears in the archaeological
record of the southwestern United States more than 3000 years ago ( 12 ),
and it is evident that cob size had already increased under selection.
The Jaenicke-Després et al . study ( 1) examines the selection of traits
that can't be observed in fossilized cobs. Taking tiny samples of fossil
cobs from the Ocampo Caves in northeastern Mexico (2300 to 4400 years
old) and the Tularosa Cave in the Mogollon highlands in New Mexico (650
to 1900 years old), the authors extracted DNA and amplified, cloned, and
sequenced small DNA fragments of the tb1 gene, the pbf gene that controls
the amount of storage protein, and the su1 gene encoding a starch-
debranching enzyme whose activity affects the texture of corn tortillas.
They compared their ancient DNA sequences with those of 66 maize
landraces (the corn grown by indigenous farmers) from South, Central, and
North America and 23 lines of teosinte parviglumis.

They report that alleles of these genes typical of modern corn were
already present more than 4000 years ago, implying that plant
architecture and kernel nutritive properties were selected early, long
before corn reached North America. All 11 ancient cobs carried the tb1
allele present in modern corn, but fewer than half of the 23 teosinte
varieties carried this allele. Similarly, all ancient samples contained a
pbf allele that is common in corn but rare in teosinte. The predominant
modern su1 allele was found in all of the older Mexican cobs, but the
younger New Mexican cobs had several different alleles, suggesting that
this gene was still undergoing selection when maize reached North America.

The authors conclude that "... by 4400 years ago, early farmers had
already had a substantial homogenizing effect on allelic diversity at
three genes associated with maize morphology and biochemical properties
of the corn cob." This suggests that once this special combination of GMs
was assembled, the plants proved so superior as a food crop that they
were carefully propagated and widely adopted, perhaps causing something
of a prehistoric Green Revolution. It also implies that the apparent loss
of genetic diversity following the introduction of high-yielding Green
Revolution wheat and rice varieties in the 1960s and 1970s, and attending
the rapid adoption of superior GM crops today, is far from a new phenomenon.

References
1) V. Jaenicke-Després et al ., Science 302 ,1206 (2003).
2) P. C. Mangelsdorf, R. G. Reeves, Proc. Natl. Acad. Sci. U.S.A. 24 ,
303 (1938).
3) J. Bennetzen et al ., Lat. Am. Antiq. 12 , 84 (2001).
4) G. W. Beadle, Sci. Am. 242 , 112 (January, 1980).
5) J. Doebley, Trends Genet. 8, 302 (1992) [Medline] .
6) S. White, J. Doebley, Trends Genet. 14 , 327 (1998) [Medline] .
7) J. Doebley et al ., Nature 386 , 485 (1997) [Medline] .
8) A. Eyre-Walker et al ., Proc. Natl. Acad. Sci. U.S.A. 95 , 4441 (1998)
[Medline] .
9) Y. Matsuoka et al ., Proc. Natl. Acad. Sci. U.S.A. 99 , 6080 (2002)
[Medline] .
10) B. F. Benz, Proc. Natl. Acad. Sci. U.S.A. 98 , 2104 (2001) [Medline] .
11) D. R. Piperno, K. V. Flannery, Proc. Natl. Acad. Sci. U.S.A. 98 ,
2101 (2001) [Medline] .
12) B. B. Huckell, J. World Prehist. 10 , 305 (1996).

The author is at the Huck Institute for Life Sciences, Pennsylvania State
University, University Park, PA 16802, USA.
E-mail: nvf1@psu.edu




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