Regulatory Sham on Bt-Crops

Regulatory Sham on Bt-Crops

By Prof. Joe Cummins, ISIS

At 80 million planted acres, corn is the largest crop grown in the US and accounts for one fifth of total agricultural cropland. Over the past years, conventional insecticides have been applied to between 14 to18 million acres of corn to control corn root worm (CRW). This single corn pest accounts for over 14% of insecticide applications to agricultural crops. Infested acreage is increasing due to extended diapause and change in the insect’s behaviour as the CRW lays its eggs in soybean fields, which are planted in rotation with corn.

Currently, the main genetically modified (GM) corn contains the Bacillus thuringiensis (Bt) toxin gene Cry1Ab to control corn borer, but does not control CRW. CRW control has been the recent focus among the corporations developing GM crops. All candidate crops are being raced to market with the cooperation of regulatory authoritatives in the US and Canada. The emphasis is on speedy evaluation and keeping down costs rather than to ensure safety to consumers and to the environment. Safety testing is done using toxins produced in bacteria acknowledged to be somewhat different from those produced in the corn plants. This is deemed to be “sound science” by the regulators.

GM corn with genes providing protection against CRW will soon reach the market. Monsanto corporation has focused on the Bt toxin Cry3Bb and has recently developed synthetic Bt toxins that combine amino acid sequences from native Cry1Ac and Cry1F crystal protein, which have enhanced broad range specificity lacking in either toxin individually. Dow corporation has been developing corn with Cry34Ab/Cry 35Ab combined toxin. Monsanto’s Cry3Bb-corn is ready for commercial release and the others will soon follow.

Patents describing the production of Bt-Cry3Bb describe the production of the synthetic Bt genes both used to produce the toxin produced in bacteria and the toxin produced in corn plants [1,2]. The synthetic Bt-cry3Bb is altered from the bacterial gene by insertion of the cauliflower mosaic virus (CaMV) promoter and enhancers, the leader sequence of wheat chlorophyll a/b binding protein, the rice actin intron, and the 3′ transcription terminator sequence of wheat heat shock protein 17.3. Along with the sequences above, many code words for amino acids were altered to enhance translation in the plant cell, and some amino acids were changed to enhance performance in the plant cell. An antibiotic resistance marker nptII, also with the CaMV promoter and the NOS transcription terminator from Agrobacterium tumefacians nopaline synthetase gene was inserted into the corn chromosome along with the Bt-cry3Bb construct The genetic insert in corn was called MON 863. The US Food and Drug Administration (FDA) noted that the Bt toxin in Mon 863 differed from the bacterial toxin by seven amino acids and by an additional amino acid, alanine in the second position from the start of the protein [3].

US Environment Protection Agency has considered a large number of documents on human health and environmental impacts of Mon 863 corn. The petition to establish a tolerance exemption for Bt-Cry3Bb argued that it was not necessary to set a tolerance level because the toxin was not toxic to mammals. But the studies supporting the exemption were done with toxin produced in bacteria that are not identical to the product in Mon 863 corn [4]. The biopesticides registration action document for event MON863 Bt-Cry3Bb1 corn provided information on product characterization [5]. The action document on environmental assessment included evidence on non-target wildlife, but reviewed data from the bacterial Bt- Cry3Bb1 toxin, and not the toxin produced in MON863 corn. EPA has also provided a fact sheet on Bt-Cry3Bb1 protein and the genetic material necessary for its production [6].

Canada approved MON863 corn for livestock feed on March 5, 2003 [7]. Limited information was provided in the Canadian decision document, and the fact that the safety investigations had been based on a product significantly different from the toxin in MON863 corn was not mentioned. The approval of GM crops bearing toxins whose safety tests have been based on tests of surrogate products appears to have grown so commonplace among regulators that it is not worthy of mention.

Dow Agroscience Corporation has been developing a binary toxin mixture containing Bt- Cry34Ab1 and Bt-cry35Ab1 effective against CRW [8,9]. Initial safety tests using toxins produced in bacteria showed that the mixture was digestible by mammals and for that reason unlikely to be allergenic [10]. The petition to EPA for tolerance exemption, and the granted temporary exemption [12] noted that the proteins were obtained from bacteria but believed to be similar to the proteins produced in corn (the product being regulated) because the products had similar gel electrophoresis mobility. The actual differences between the synthetic genes in corn and the protein they produce and the protein toxins produced in bacteria from the native gene have not yet been disclosed.

Monsanto recently (Nov. 11,2003) disclosed methods for the construction of B. thuringiensis hybrid delta-endotoxins comprising amino acid sequences from native Cry1Ac and Cry1F crystal proteins. These hybrid proteins, in which all or a portion of Cry1Ac domain 2, all or a portion of Cry1Ac domain 3, and all or a portion of the Cry1Ac protoxin segment is replaced by the corresponding portions of Cry1F, possess not only the insecticidal characteristics of the parent delta-endotoxins, but also have the unexpected and remarkable properties of enhanced broad-range specificity not displayed by either of the native delta-endotoxins. The hybrid toxins incorporated into transgenic plants express broad-spectrum insecticidal activity against a variety of coleopteran, dipteran, and lepidopteran insects [13]. Presumably, the deployment of the synthetic genes, described above, is meant to provide protection against all of the major insect pests of corn. It seems likely that the mammalian toxicity tests and the test of impact on non-target animals will be done with the protein produced in bacteria not the one produced in corn plants.

In spite of the clear differences between the genes and the insecticide toxin proteins produced in bacteria and those produced in transgenic plants the US and Canadian regulators have agreed with the corporations manufacturing the GM crops that the products are substantially equivalent. So long as the final toxins are similar the bacterial toxins can be used as surrogates for the crop toxin in safety testing. The regulators made little or no effort to directly test the validity of their presumptions. They are placing the burden of proof that the toxins in the GM crops are unsafe for mammals and the environment on the shoulders of the public, not the corporations who profit from the GM crops. In the final analysis, the regulators are providing essential public relations benefits for the corporations but not adequately protecting the public. And so long as GM crops are not labeled in the market, the errors of the regulators will go undetected.

1.Romano C. Expression of Cry3B insecticidal proteins in plants, 2002 US patent 6 501 009 155pp.

2.English L, Brussock S, Malvar, T, Bryson J, Kulesza C, Walters F, Slatin S, Von Tersch M and Romano C. Coleopteran-resistant transgenic plants and methods of their production using modified Bacillus thuringiensis Cry3Bb nucleic acid. 2003 US patent 6 620 988.

3. US Food and drug Administration Center for Food safety and Applied Nutrition Office of Food Additive safety. “Biotechnology consultation note on the file BNF No. 000075”,
2001 pp. 1-4

4.US Environmental Protection Agency “Bacillus thuringiensis Cry3Bb1; Notice of filing a pesticide petition to establish a tolerance exemption for a certain pesticide chemical in or on food”, 2003 Federal Register 68 60371-5

5.US Environmental Protection Agency “Event MON863 Bacillus thuringiensis Cry3Bb1 Corn” 2003 Biopesticides registration Action Document pp1-34 ; C. Environmental Assessment” Biopesticides registration Action Document pp1-43

6. US Environmental Protection Agency “Bacillus thuringiensis Cry3Bb1 protein and the genetic material necessary for its production (Vector ZMIR13L) in Event MON863 corn fact sheet” 2003. pp1-20

7.Canadian Food Inspection Agency Plant Biosafety Office, “Decision Document DD2003-43: Determination of the safety of Monsanto Canada Inc.’s Insect Resistant Corn (Zea Mays L.) line MON863”, 2003 pp1-15

8. Herman R, Scherer P,Young D, Mihaliak C, Meade T, Woodsworth A, Sockhoff B and Narva K Binary insecticidal protein from Bacillus thuringiensis , strain PS149B1: Effects of individual proteins and mixtures in laboratory bioassays. J.Econ. Entomol 2002, 95, 635-9

9.Ellis R, Stockhoff B, Stamp L, Schnepf H, Schwab G, Knuth M, Russel J, Cardineau G and Narva K. Novel Bacillus thuringiensis binary insecticidal crystal protein active on western corn root worm. Appl and Environ Microbiol 2002, 68,1137-45.

10. Herman R, Schafer B, Korjagin V and Ernest A. Rapid digestion of Cry34Ab1 and Cry35Ab1 in simulated gastric fluid. J.Agric Food Chem 2003, 51,6823-711.

11.US Environmental Protection Agency “Notice for filing a pesticide petition to establish tolerance for a certain pesticide chemical in or on food” 2003 Federal Register 68 11100-3.

12. US Environmental Protection Agency “Bacillus thuringiensis Cry34Ab1 and Cry 35Ab1 proteins and genetic material necessary for their production in corn; Temporary exemption from requirements of tolerance” 2003 Federal Register 68 40178-83

13. Malvar T and Gilmer A. “Polynucleotide compositions encoding broad spectrum delta endotoxins” US patent 6 645 497 pp1-161

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