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'Terminator' Technology

    Harvesting cotton in Burkina Faso.
    Photo: Alfred Schwartz © IRD

    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.

    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.

    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)
    ( 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.

    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.

    Cotton boll.
    Photo: www.mahyco.com

    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
    also discuss the Terminator.

    Jason Sutton from the Department of Bioagricultural Sciences and Pest Management at Colorado State University contributed to this report.

Page last updated : February 2, 2004

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