Will Plants with Terminator-Type Genes Prevent Replanting of Genetically Engineered Crops?

The Rural Advancement Foundation International [RAFI, now ETC (Erosion, Technology, and Conservation) Group] (1) first used the term “terminator technology” in 1998 in a patent issued jointly to Delta & Pine Land Company and the USDA (2). This technology was described as a means to restrict reuse of GE seeds; second-generation seeds would be sterile (3) and could not germinate (4).

Terminator technology is one form of GURT; there are two types,V-GURTs (varietyprotected GURTs) and T-GURTs (traitspecific GURTs). An example of plants with V-GURTs would be those with terminator technology. Because saved seeds would not germinate, users would have to repurchase seeds each year—similar to the situation with hybrid crops that must be purchased yearly to realize yield advantages (5). Hybrid seed use, which represented 95% of U.S. corn acreage in 2006 (6), would not be affected by the use of terminator technology and users’ having to repurchase seeds because farmers using hybrid seed must already repurchase seed each year. Crops engineered with T-GURTs must be treated with specific chemicals for the engineered trait to be expressed. In this case, farmers could replant seed but would lose the advantage of the trait if their crop was not treated with the chemical, something RAFI termed “traitor technology.”

Terminator technology was complex as patented, involving several genes, with one stopping protein synthesis and preventing seed germination. So that the planted seed could initially grow, this gene product was not expressed in the first generation, but was instead halted by a spacer gene under control of the cre/lox system. Cre recombinase excised the spacer, straddled by lox excision signal sequences, which activated expression of a second gene, which halted germination and encoded a ribosomal inhibitor protein (RIP), under control of a third gene product for the TN10 tetracycline repressor. Use in tobacco and cotton was described in the patent as functional but efficacy was not shown. The system required functional and timed expression of three genes, making it problematic as a commercial approach, and in fact, the system has not been commercialized.

Terminator technology has been criticized by some farmer and consumer groups as potentially disastrous for food security and biodiversity (7). After criticisms surfaced in 1999, Monsanto, then owner of the technology, vowed not to use it; other seed companies also agreed. Controversy over the technology reignited in 2005 because of a statement in Monsanto’s Pledge Report to Stakeholders, “Monsanto does not rule out the potential development and use of one of these technologies in the future” (8). This controversy led to the introduction of a bill into the Canadian Parliament in May 2007 to “prohibit field testing and commercialization of Terminator seed technology.” In May 2008 worries surfaced that a global ban on terminator technology would be rescinded at a United Nations’ summit on genetic diversity, but the issue was not discussed (9). One concern raised aboutV-GURTplants is that they would cross-pollinate with non-GE plants such as compatible wild relatives or crops in fields of farmers not wishing to adopt GE crops, and become sterile. Although V-GURT plants were sterile, some worried that the sterility trait would occasionally not be expressed, become activated, and cause sterility. Given the complexity of the technology, sterility in non- GE plants caused by cross-pollination would be highly unlikely to occur.

A positive aspect to using such technologies is to inhibit effectively the flow of undesirable GE traits to compatible relatives. It might be prudent, for example, to limit the flow of genes that could give growth or pest-resistance advantages to wild relatives or that encode vaccines, antibodies, or industrial chemicals. Use of VGURTs thus would slow the movement of GE traits, which could be particularly important in regions of high genetic diversity.

References:

1. Rural Adv. Found. Int. 1999. RAFI’s Impact: 1999. Insert to 1998/99 RAFI Annual Report. http://www.etcgroup.org/upload/report/12/01/99rafiimpact.pdf. Last accessed 2011-12-12. PDF

2. Wacek T. 1998. Patent awarded for plant gene expression. ISB News Rep. Aug.:1–2

3. Oliver MJ, Quisenberry JE, Trolinder NLG, Keim DL. 1998. Control of plant gene expression. U.S. Patent 5723765

4. Gupta PK. 1998. The terminator technology for seed production and protection: Why and how? Curr. Sci. 75:1319–23

5. Fowler C. 1994. Unnatural Selection: Technology, Politics and Plant Evolution. Yverdon, Switz.: Gordon & Breach Sci.

6. USDA-ARS. 1962. ARS Timeline: Improving Corn. http://www.ars.usda.gov/is/timeline/corn.htm. Last accessed 2011-12-12. PDF

7. Service RF. 1998. Seed-sterilizing ‘terminator technology’ sows discord. Science 282:850–51

8. Monsanto. 2005. Pledge Report. http://www.monsanto.com/ourcommitments/Documents/CSR_reports/MonsantoPledgeReport-2005.pdf. Last accessed 2011-12-12. PDF

9. Conv. Biol. Divers. 2008. Rep. 4th Meet. Conf. Parties Conv. Biol. Divers. Meet. Parties Cartagena Protocol Biosafety (COP-MOP/4), Bonn, May 12–16

Updated 2/16/12