Harvesting cotton in Burkina Faso.
Photo: Alfred Schwartz © IRD
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One potential use for transgenic technology is to
allow seed producers to realize profits from their
investments in new product development. For many decades,
seed companies have preferred to invest heavily in
developing new varieties of crops such as corn for
which the farmer typically purchases new seeds each
year. Seed companies have invested less in crops such
as wheat for which the farmer traditionally saves
a portion of his harvest each year to use in planting
his fields the following year. (Why
save seeds versus buying new seeds?)
Several plant patent laws were passed during the
last century in an attempt to increase the potential
profit to agricultural and horticultural businesses
that develop new varieties, but enforcement of the
protection can be inconvenient and many companies
have not found it profitable when protection cannot
be assured. Two biotech protection methods, dubbed
'Terminator' and 'Traitor' by opponents, may allow
companies to increase profits on their cultivar development
efforts.
Important landmarks in U.S. patent law
Plant
Patent Act of 1930
Plant
Variety Protection Act of 1970
- 1980 amendment
- 1994 amendment
Utility
Patents |
'Terminator,' officially named the Technology Protection System
(TPS), incorporates a trait that kills developing plant embryos,
so seeds cannot be saved and replanted in subsequent years.
'Traitor,' officially known as Trait-specific Genetic
Use Restriction Technology or T-Gurt, incorporates a control
mechanism that requires yearly applications of a proprietary
chemical to activate desirable traits in the crop. The farmer
can save and replant seeds, but cannot gain the benefits
of the controlled traits unless he pays for the activating
chemical each year.
Both methods avoid the difficulties associated with enforcing
"no replanting" agreements. Because TPS and T-Gurt plants
would be transgenic, their commercial use will require approval
by the government.
How Does the Technology Protection System Work?
The Technology Protection System (TPS) inserts half a dozen
sequences into the DNA of the parent plant that is slated
for protection. These DNA sequences are arranged into a
system that kills seeds at a prearranged time in their development.
The system can be left inactive while the seed company grows
several generations of seeds for sale. The system is switched
on by soaking the seeds in a special chemical before the
seeds are delivered to the farmer for planting.
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The special chemical triggers a slow cascade of events
that lead eventually to the death of progeny seeds
developed on the protected plant.For the purpose of
preventing replanting, the progeny seeds should be
killed only after they have completed production of
all commercially valuable products such as oil. Therefore,
the system is designed to take effect only after the
crop has grown to maturity in the field and the progeny
seeds are nearly ripe.
Many combinations of foreign genes can be used, so
the list of all possible genes is quite long. Below
is one system that was discussed extensively in the
TPS patent.
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|
| name of DNA sequence |
source |
purpose |
35S promoter
( in diagram,
gene 2) |
cauliflower mosaic virus |
switches on the gene connected to it |
Tn10 tet repressor
( in
diagram) |
Escherichia coli,
a bacterium |
prevents recombinase from being made (see
"cre recombinase" below in this table)
|
cre recombinase
(scissors in diagram) |
P1 virus |
cuts out the lox segments
that block production of the ribosomal inhibitor (see
"lox" below in this table) |
lox
( in
diagram) |
could be native to the host plant or derived
from another organism |
creates a barrier to the production of
ribosomal inhibitor; removal of the lox segments allows
the production of ribosomal inhibitor (see "ribosomal
inhibitor" below in this table) |
late embryogenesis promoter
( in diagram,
gene 3) |
could be native to the host plant or derived
from another organism |
stimulates production of the ribosomal
inhibitor when the seeds reach a late stage of development
(see "ribosomal inhibitor" below in this table) |
ribosomal inhibitor protein
(skull and crossbones in diagram) |
Saponaria officinalis,
a plant |
kills the developing seeds by stalling
the essential process of making proteins |
Who Developed the Technology Protection System?
Scientists from the Agricultural Research Service, a subunit
of the US Department of Agriculture (USDA-ARS), and Delta
and Pine Land Company, a company that develops cotton cultivars,
jointly developed the system and on March 3, 1998, were
awarded a joint patent
(number 5,723,765) entitled Control of Plant Gene Expression.
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The research was conducted under a Cooperative Research
and Development Agreement (CRADA) signed in 1993 between
Delta and Pine Land Company and the ARS. Laws dictate
that government-owned inventions made under a CRADA
will be licensed exclusively to the cooperator, in
this case to Delta and Pine Land. The USDA-ARS says
it will be active in deciding how the technology is
applied to ensure that the public interest is represented.
Delta and Pine Land Company estimates that the earliest
date for a TPS cotton cultivar would be 2004.
Read more about the development circumstances on
the USDA-ARS's web page at http://www.ars.usda.gov/is/br/tps/#status.
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Cotton boll.
Photo: www.mahyco.com
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Potential Benefits of the Technology Protection System
- Companies may develop improved crop varieties
The USDA-ARS and Delta and Pine Land Company say the technology
will encourage seed companies to pursue variety development
more vigorously, especially in "minor crops" for which
seed companies typically do not expend a large amount
of money in research. If a seed company knows it will
be able to "protect its investment" in the development
of new varieties, including transgenics, by preventing
farmers from saving seed and replanting from year to year,
more effort will be put into the development of improved
varieties.
- Transgenic crops with TPS will not spread their genes
to surrounding plants
The TPS genes are transferred on pollen, so any plant
pollinated by a TPS plant will produce dead seeds. This
would prevent accidental gene flow from transgenic crops
to wild plant populations. (See
below for a related risk of killing wild seeds.)
Potential Risks of the Technology Protection System
- Pollen from TPS plants may kill neighboring crop
seeds
Pollen from TPS plants may fertilize non-TPS crops in
neighboring fields, resulting in the unintentional death
of seeds in the non-TPS crop. The USDA-ARS and Delta and
Pine Land Company say the risk of this will be low because
TPS technology is intended for highly self-pollinating
crops; therefore, pollination from adjacent fields is
unlikely. However, research is underway to develop TPS
crops that do not carry any transgenic genes on the pollen,
preventing unwanted transfer of the trait.
- Pollen from TPS plants may
kill neighboring wild plant seeds
While this can be viewed as a benefit in preventing the
spread of transgenic traits to wild populations, it may
have a negative impact on the ability of wild populations
to maintain themselves. Depending on the propensity of
the crop for crossing to wild populations, some rare or
endangered plant populations might be threatened by the
presence of TPS crops. Case-by-case consideration will
be needed.
- Small farmers may suffer economic harm
Small farmers who have depended on the ability to replant
seeds from year to year may be hurt because they will
have to buy new seeds each year. Several organizations,
including the Union of Concerned Scientists, are especially
troubled by the implications of this technology in the
developing world, where seed saving is a more common practice
than in the United States. According to a Terminator Technology
article on the Union of Concerned Scientists web page
(http://www.ucsusa.org/publication.cfm?publicationID=267),
"poor farmers are especially alarmed at the prospect of
seed markets dominated by multinational corporations selling
sterile seeds." The article also states that "they (the
poor farmers) fear increased seed costs and loss of control
over their own food supplies." Hope Shand from ETC Group,
an advocacy group opposed to genetically engineered crops,
claimed that "The ultimate goal of seed sterility is neither
biosafety nor agronomic benefits, but bioserfdom." A news
release from ETC Group is available at http://www.rafi.org/article.asp?newsid=312.
- The method used to kill the seeds may harm other
organisms
The TPS patent notes that the ribosome inhibitor is the
preferred agent for killing seeds because it is not lethal
to people who might eat the seeds. However, the patent
authors suggest that "any lethal gene should be acceptable"
in cases where there is no use for the seeds. They suggest
that diphtheria toxin or any cytotoxic protein could be
used for the purpose. (See "Example 1, Selection
of Lethal (RIP) coding sequence" in the patent.)
Seed companies and government regulators may want to consider
the possible impact on seed-eating birds, insects, and
micro-organisms.
- The chemical treatment may have negative impacts
on the environment
The patent authors envision using the antibiotic tetracycline
to trigger the TPS system. Large-scale use of this antibiotic,
used to treat human diseases, may cause an increase in
antibiotic resistance in bacteria in the environment.
Technology Protection System versus Trait-specific Genetic
Use Restriction Technology
Because of the controversy surrounding TPS technology, several
agro-chemical companies are developing an alternative called
T-Gurt. This is still a transgenic system, but one that
may raise fewer objections than TPS.
How Does Trait-specific Genetic Use Restriction Technology
Work?
Unlike TPS seeds, T-Gurt seeds will not have controlled
sterility and will be able to be planted year after year
by farmers. However, in order for the farmer to benefit
from the genetically modified traits inserted into the genome,
the farmer must purchase a proprietary chemical each year
to spray on the seeds or young plants to activate the trait
if he saves seeds for replanting.
Who Is Developing the T-Gurt System?
Agro-chemical companies including Monsanto and AstraZeneca
are developing T-Gurt.
Potential Benefits of Trait-specific Genetic Use Restriction
Technology
- The T-Gurt traits would not be activated in wild
populations
If T-Gurt pollen were to accidentally fertilize nearby
wild plants, the traits controlled by the T-Gurt system
would not be activated in wild seeds because the proprietary
chemical would not be present in the natural environment.
The DNA for the new traits would be transferred to wild
populations, but the traits would not be expressed.
- Subsistence farmers would be able to replant seeds
from year to year
Although they would not gain the benefit of the engineered
traits unless they bought the proprietary chemical each
year, subsistence farmers would have the choice of follow
traditional replanting practices.
Richard Jefferson, director of the Center for the Application
of Molecular Biology to International Agricultural in Canberra,
Australia, sees T-Gurts as "a compromise technology
that meets industry's desire to protect intellectual property
and maximize returns on innovations in agricultural biotechnology
without jeopardizing the practice of subsistence farmers
using seeds from a crop for planting in the future."
(Masood
1999, http://www.nature.com/wcs/b50.html)
Potential Risks of Trait-specific Genetic Use Restriction
Technology
- Pollen from T-Gurt plants may fertilize neighboring
crops
If nearby organic crops were fertilized by pollen from
T-Gurt plants, the resulting seeds would test positive
for the presence of transgenic DNA sequences and could
not be sold as organic. As in the discussion of this risk
for TPS plants above, if the technology is used for highly
self-pollinating crops, the risk of pollination from adjacent
fields is low. As with TPS plants, if a cultivar can be
developed that does not carry transgenes on the pollen,
unwanted spread of transgenes would be avoided.
- The chemical treatment may have negative impacts
on the environment
The proprietary chemical used to treat the seeds each
year should not be one that has negative consequences
for the environment. Developers and government regulators
may want to consider the environmental safety of the chemical
when designing and approving T-Gurt cultivars.
Other Resources
The patent for the Technology Protection System is available
at http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=
HITOFF&d=PALL&p=1&u=/netahtml/srchnum.htm &r=1&f=G&l=50&s1=5,723,765.WKU.&OS=
PN/5,723,765&RS=PN/5,723,765.
"How the Terminator Terminates" by Dr. Martha L. Crouch
is an excellent discussion of how the process works and
some potential risks. http://www.biotech-info.net/howto.html
Terminator Technology for Transgenic Crops contains a discussion
and diagram of the process. http://filebox.vt.edu/cals/cses/chagedor/terminator.html
Emerging Biotechnologies: Upgrading the Terminator
http://www.isb.vt.edu/news/2002/news02.nov.html#nov0202
and
Re-emerging Biotechnologies: Rehabilitiating the Terminator
http://www.isb.vt.edu/news/2002/news02.jun.html#jun0203
also discuss the Terminator.
Jason Sutton from the Department of Bioagricultural
Sciences and Pest Management at Colorado State University
contributed to this report.
'Terminator'
Technology 