Science in Society Archive

GM Maize 59122 Not Safe

Dismissing differences detected between GM and non-GM feed in safety tests appears to be common practice, and is condoned by regulatory authorities. Prof. Joe Cummins and Dr. Mae-Wan Ho

This report has been submitted to the European Food Safety Authority public consultation on behalf of I-SIS.

Double-whammy GM maize gets positive opinion from European Food Safety Authority

Maize 59122 is genetically modified for rootworm protection and herbicide tolerance, and has been developed by Dow Chemical and its associated company Pioneer Hybrid Seed Company. The variety is based on the gene transformation event DAS-59122-7, expressing unique binary proteins Cry34Ab1 and Cry35Ab1 derived from the soil bacterium Bacillus thuringiensis (Bt) Herculex. DAS-59122-7, and the PAT protein conferring resistance to the herbicide glufosinate ammonia. The transgenes, along with control elements including promoters and terminators, are inserted at a single locus in a maize chromosome [1]. The company has applied to place Maize 59122 on the market in Europe for use as food, feed, processing, and other products, and the European Food Safety Authority (EFSA) has put out its opinion [2] for public comment. Unsurprisingly, the EFSA considers maize 59122 “unlikely to have any adverse effect on human and animal health or on the environment in the context of its intended uses.”

Simultaneously the company has applied to Canada, China, Japan and Korea for import and environmental release, and to Mexico, Taiwan and Australia/New Zealand for food use.

Dow Agrisciences/Pioneer Hybrid International had submitted an application for non-regulated status for the same transgenic maize to the United States Department of Agriculture Animal and Plant Health Inspection Service (USDA/APHIS) in December 2003 [3], and the transgenic maize is currently marketed in the US as Herculex RW.

The application to Europe indicated that event 59122, created by Agrobaterium-mediated transformation, had incorporated synthetic approximations of three genes: Cry34Ab1 with a maize ubiquitin promoter and intron and a terminator sequence from potato protease inhibitor II; Cry35Ab1 with a wheat peroxidise promoter and terminator from potato protease inhibitor II; and PAT for glufosinate tolerance with 35S CaMV promoter and terminator. The application also claimed that the genes were stably inserted at a single locus and there was no evidence of instability. The application also stated that the transgenes were incorporated correctly between the left and right borders of T-DNA, and that 59122 maize does not contain fragments from the vector backbone [2]. However, the claim to stability appears to depend on a Southern blot analysis within a single plant breeding generation.

The application claims a “very broad body of evidence” for the safety of the transgenic proteins in food and feed. So let’s look at the evidence.

Safety assessment based on surrogate proteins fundamentally flawed

The proteins synthesized from the artificial genes were compared with proteins synthesized in bacteria and seemed identical (but see later). The main safety and environmental tests were therefore done on proteins derived from bacteria, and not from the transgenic maize.

USDA/APHIS conducted an environment assessment of maize event 59122 - its potential impacts on non-target organisms including threatened and endangered species – and concluded the environmental effects insignificant [4]. However, the bulk of the tests were done also with proteins isolated from bacteria, not from maize 59122. A fuller comparison of the insecticidal proteins produced in 59122 with those in the bacteria used in safety testing revealed that four amino acids in the C-terminal domain were different in Cry35Ab1. But these differences were considered negligible [5].

In general, the C-terminal domain of Bt toxins is involved in structural stability, ion channel gating, binding to membrane vesicles and determining insecticidal specificity [6]. A study of Cry34/Cry35 insecticidal proteins from diverse Bt strains showed that Cry 35Ab1

contains a segment similar to the to a beta-trefoil domain that may be a binding motif for galactose [7]. Some examples of trefoil domains include those in the toxins from Clostridium botulinum, abrin and ricin [8]. It seems very cavalier of the USDA to ignore amino acid sequences in a domain known to be active in important functions, and the EFSA is doing likewise.

Transgenic maize not substantially equivalent to non-transgenic variety

Maize 59122 was analysed and compared with near-isogenic non-GM maize lines to determine whether or not 59211 was substantially equivalent to unmodified maize. The maize lines were compared for fibre and minerals, for amino acids, fatty acids, vitamins, secondary metabolites and anti-nutrients. One parameter, carbohydrate, was significantly lower in 59122 treated with glufosinate; and 13 of 65 (20 percent) determinants, including forage fibre, grain amino acids and vitamins, were outside the levels for conventional maize. The expected level for differences solely due to chance is just over 3 out of 65 (5 percent). In spite of these many differences, 59122 was deemed substantially equivalent to unmodified maize [9].

Feeding studies inadequate

A sub-chronic study was carried out for 90 days on rats fed 59122 grain compared with grain from a near isogenic line. For the most part the differences between animals fed 59122 maize and non-GM maze were not significant.  Nevertheless, significant differences were detected in the levels of mean corpuscular haemoglobin, haemoglobin concentration, red cell width, reticulocyte count and platelet count; but these blood values were ignored [10]. Chickens were fed grain either from 59122 or from a near-isogenic maize. Carcass and organ weights were measured after 42 days. For the most part, carcass and organ sizes were not different, though the livers of female chickens fed transgenic maize were significantly enlarged, but that, too, was ignored [11].

Significant differences ignored and regulators turn a blind eye

It has now become customary for company researchers to pass over significant differences due to the consumption of GM feed in animal testing, and for regulators to condone such fraudulent practices, as is clear in the recent re-analysis of Monsanto’s MON 863 feeding study by independent scientists [12] (GM Maize MON 863 Toxic, SiS 34). The significant differences between 59122 and near isogenic maize lines, detected even when only relatively crude parameters were measured, obviously cry out for fuller independent studies, and highlight the inadequacy of current regulatory regimes [13] (GM Food Nightmare Unfolding in the Regulatory Sham, ISIS scientific publication, also SiS 33).

The use of proteins produced in bacteria as surrogates for transgenic proteins in toxicity and other safety tests is not acceptable. In addition to a thorough characterization of the transgenic proteins and its mechanism of action in insects and mammals, there must also be long term feeding trials with the transgenic maize similar to those carried out for drugs and pesticides [12]. A full safety evaluation should further include characterizations using micro-array technology, now available for maize [14], which would be a great improvement on the kind of equivocal results used for the claim that 59122 is ‘substantially equivalent’ to non-GM maize and hence ‘safe’.

In conclusion, maize 59122 has not passed its safety test, and should not be given market approval.

Article first published 19/04/07



References

  1. The Dow Chemical Company Product Safety Assessment Herculex RW Rootworm Protection 2006, http://www2.dupont.com/Biotechnology/en_US/products/herculex_rw/safety2.html
  2. Open Consultations Europa –Food Safety, http://ec.europa.eu/food/food/biotechnology/authorisation/public_comments_en.htm
  3. Hunst P and Rood T..Application for the Determination of Nonregulated Status for Bt Cry34/35 Ab1 insect resistant Glufosinate-Tolerant Corn: Corn Line 59122 2004, http://www.aphis.usda.gov/brs/aphisdocs/03_35301p.pdf
  4. Smith C. Environment Assessment for Dow/Pioneer Rootworm Resistant Corn 2005, http://www.aphis.usda.gov/brs/aphisdocs2/03_35301p_com.pdf
  5. Gao Y, Schafer BW, Collins RA, Herman RA, Xu X, Gilbert JR, Ni W,Langer V and Tagliani LA. Characterization of Cry34Ab1 and Cry35Ab1 insecticidal crystal proteins expressed in transgenic corn plants and Pseudomonas fluorescens. J Agric Food Chem. 2004, 52(26), 8057-65.
  6. Saraswathy,N and Kumar,P. Protein engineering of delta endotoxins of Bacillus thuringiensis Electronic Journal of Biotechnology Microbial Biotechnology 2004, 2,1-12. http://www.ejbiotechnology.info/content/vol7/issue2/full/3/index.html
  7. Schnepf HE, Lee S, Dojillo J, Burmeister P, Fencil K, Morera L, Nygaard L, Narva KE and Wolt JD. Characterization of Cry34/Cry35 binary insecticidal proteins from diverse Bacillus thuringiensis strain collections. Appl Environ Microbiol. 2005, 71(4),1765-74.
  8. Mancheno JM, Tateno H, Goldstein IJ, Martinez-Ripoll M and Hermoso JA. Structural analysis of the Laetiporus sulphureus hemolytic pore-forming lectin in complex with sugars. J Biol Chem. 2005, 280(17),17251-94.
  9. Herman RA, Storer NP, Phillips AM, Prochaska LM and Windels P. Compositional assessment of event DAS-59122-7 maize using substantial equivalence. Regul Toxicol Pharmacol. 2007, 47(1),37-47.
  10. Malley LA, Everds NE, Reynolds J, Mann PC, Lamb I, Hood T, Schmidt J, Layton RJ, Prochaska LM, Hinds M, Locke M, Chui CF, Claussen F, Mattsson JL and Delaney B. Subchronic feeding study of DAS-59122-7 maize grain in Sprague-Dawley rats. Food Chem Toxicol. 2007 In press doi:10.1016/j.fct.2007.01.013
  11. McNaughtona J, Robertsa M, Riceb D, Smith B, Hindsb M, Schmidtb J, Lockec M, Bryant A, Rood.T, Laytonb R, Lamb I and Delaneyb B. Feeding performance in broiler chickens fed diets containing DAS-59122-7 maize grain compared to diets containing non-transgenic maizegrain Animal Feed Science and Technology 2007,132, 227-239.
  12. Ho MW, Cummins J and Saunders PT. GM food nightmare unfolding in the regulatory sham. Microbial Ecology in Health and Disease 2007 (in press); also Ho MW. GM food nightmare unfolding and the regulatory sham. Science in Society 33, 32-35, 2007.
  13. Ho MW. GM maize MON 863 toxic. Science in Society 34 (in press).
  14. Shi C, Thümmler F, Melchinger A, Wenzel G and Lübberstedt.T. Comparison of transcript profiles between near‐isogenic maize lines in association with SCMV resistance based on unigene-microarrays. Plant Science 2006, 170,159-169

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