ARCHIVED - Novel Food Information
ARCHIVED - High Lysine Corn LY038
Health Canada has notified Monsanto Canada Inc. that it has no objection to the sale of food derived from corn lines containing the transformation event LY038 that confers elevated levels of free lysine predominately in in the germ portion of the grain. The Department conducted a comprehensive assessment of this corn event according to its Guidelines for the Safety Assessment of Novel Foods. These Guidelines are based upon internationally accepted principles for establishing the safety of foods with novel traits.
The following provides a summary of the notification from Monsanto, and the evaluation by Heath Canada and contains no confidential business information.
Monsanto Canada Inc. in collaboration with Renessen LLC developed a genetically modified corn with elevated levels of free lysine in grain.
Corn event LY038 was developed using recombinant DNA technology, resulting in the introduction of the bacterial gene cordapA from Corynebacterium glutamicum. This gene encodes the lysine-insensitive dihydrodipicolinate synthase (cDHDPS) enzyme. Dihydrodipicolinate synthase (DHDPS) is a regulatory enzyme in the lysine biosynthetic pathway and is the first and major rate-limiting enzyme for lysine biosynthesis in plants and bacteria. As the first committed enzyme in lysine biosynthesis, DHDPS is highly susceptible to lysine feedback inhibition, particularly DHDPS isolated from plants. Since the cDHDPS enzyme is less sensitive to lysine feedback inhibition, its expression in corn LY038 is expected to result in the elevated levels of free lysine in the plant when compared to conventional corn. The transcription of cordapA is under the control of the corn promoter globulin 1 (Glb1) which directs cDHDPS expression predominantly in the germ, resulting in accumulation of free lysine in this portion of the grain.
Currently, all commercially grown corn exhibiting the high lysine trait are derived by conventional breeding of corn mutants with reduced accumulation of lysine-poor zein seed storage proteins and increased accumulation of other storage proteins with higher lysine content in the endosperm portion of the grain. In contrast to the protein-bound lysine of such mutants, the elevated lysine content of corn LY038 is achieved by the accumulation of free lysine amino acids in the germ portion of the grain.
LY038 corn is intended for import to Canada from the US as a nutritionally enhanced livestock feed ingredient only. The use of LY038 corn grain in animal feeds provides an alternative to the direct addition of commercially available supplemental lysine sources in the form of lysine monohydrochloride or lysine sulphate, which are produced via fermentation by Corynebacterium glutamicum or Brevibacterium lactofermentum.
The safety assessment performed by Food Directorate evaluators was conducted according to Health Canada's Guidelines for the Safety Assessment of Novel Foods. Although not intended for human food use, the assessment was performed to account for potential accidental co-mingling of LY038 corn with conventional corn in the food supply. The assessment considered: how corn event LY038 was developed; how the composition and nutritional quality of corn grain derived from plants containing this event compare to non-modified corn; and what the potential is for food products derived from plants containing this event to be toxic or cause allergic reactions.
The Food Directorate has a legislated responsibility for pre-market assessment of novel foods and novel food ingredients as detailed in Division 28 of Part B of the Food and Drug Regulations (Novel Foods). Foods derived from corn lines containing event LY038 are considered novel foods under the following part of the definition of novel foods: "c) a food that is derived from a plant, animal or microorganism that has been genetically modified such that
i) the plant, animal or microorganism exhibits characteristics that were not previously observed in that plant, animal or microorganism".
2. Development of the Modified Plant
Corn event LY038 was developed through biolistic particle bombardment transformation of corn embryo derived tissue followed by negative selection on culture media containing the antibiotic kanamycin. The transforming sequences comprised of two tandem expression cassettes, one for the cDHDPS encoding cordapA gene and one for the antibiotic resistance marker gene nptII.
The cordapA gene cassette contained the corn Globulin 1 promoter (P-Glb1), the rice actin 1 intron sequence (I-ract1), the chloroplast transit peptide derived from the dihydrodipicolinate synthase of corn (TP-mDHDPS), the coding region of the dihydrodipicolinate synthase gene from Corynebacterium glutamicum (cordapA), and the 3' untranslated region of the Globulin1 gene from corn (Glb1 3'UTR).
The nptII cassette was flanked by bacteriophage P1 derived lox sequences, and was subsequently excised using the Cre/lox recombinase system upon conventional cross breeding with a corn line expressing the Cre recombinase encoded by an expression cassette for the bacteriophage P1 derived cre gene. Corn event LY038 specifically refers to a single breeding progeny segregant following Cre/lox recombination that contains only the cordapA gene cassette, and not any other transgenes.
3. Characterization of the Modified Plant
Southern blot and PCR analysis of corn containing the event LY038 demonstrated the insertion of one copy of the cordapA gene cassette in the corn genome. Southern blot analysis also demonstrated the integrity of the cordapA gene and regulatory elements, and the absence of the nptII and cre expression cassettes and any plasmid-derived sequences in the final LY038 genome.
The stability of the inserted cordapA expression cassette was evaluated in multiple generations of corn LY038. Trait segregation data from five generations demonstrated stable Mendelian inheritance at the phenotypic level, while Southern blot analysis from six generations demonstrated genetic stability at the genotypic level.
4. Product Information
Corn event LY038 differs from its traditional counterparts by the addition of the cordapA gene cassette sequences from Corynebacterium glutamicum into the corn genome. This gene encodes the lysine-insensitive dihydrodipicolinate synthase (cDHDPS) enzyme. The recombinant enzyme encoded by the cordapA gene is expressed predominantly in the germ portion of the grain.
5. Dietary Exposure
Expression levels of cDHDPS protein in LY038 grain as determined from replicated field trials across five sites averaged 26 μg/g on a dry weight basis. Corn event LY038 is intended for importation to Canada from production areas in the US for use as livestock feed only, and is not intended for human consumption.
Compositional equivalence of corn event LY038 to the "negative segregant control" LY038(-), which has background genetics representative of LY038, from five replicated sites in the US was assessed along with 20 commercial corn varieties. Forage and grain samples were analyzed for proximate, fibre, amino acids, fatty acids, minerals, vitamins and secondary metabolites.
The nutrient and antinutrient data for LY038 corn provided by the petitioner have shown that with the exception of total lysine and lysine-related catabolites: saccharopine and α-aminoadipic acid, LY038 corn grain is comparable in composition with grain obtained from the LY038(-) control and with grain from commercial corn.
As intended, the levels of lysine in LY038 corn grain were significantly higher than levels in LY038(-) grain. The increase in lysine concentration does not improve the protein quality, in terms of human protein requirements. Even though the concentration of lysine is increased by approximately 40% in LY038, the increase does not result in a change in the Protein Rating. This is because the starting rating is low, and the concentration of the next limiting amino acid(s) remain low. There is also no adverse impact expected from the increase in lysine content.
The potential for toxicity for the cDHDPS enzyme expressed in corn lines containing event LY038 was considered remote. This conclusion was based on the low amount of cDHDPS found in corn grain, the absence of demonstrated acute toxicity to cDHDPS in mice at doses orders of magnitude greater than the range associated with proteins, the lack of sequence homology between known toxins and the cDHDPS enzyme, and the likelihood that the cDHDPS will be degraded under conditions similar to those in the human gastrointestinal tract. There were no additional health concerns regarding endogenous toxins from food products derived from corn lines containing event LY038 when compared to non-transgenic varieties.
The possibility that the cDHDPS enzyme would be allergenic in corn lines containing event LY038 was also considered unlikely. This was based on the lack of sequence homology of cDHDPS to any known allergens, and the rapid digestion of the enzyme in simulated gastric fluids. These results suggest that foods derived from corn lines containing event LY038 would not pose any greater allergenic risk than non-transgenic corn.
The available evidence suggests that the elevated levels of lysine and associated naturally occuring catabolites such as saccharopine and α-aminoadipic acid observed in LY038 grain are unlikely to be of toxicological concern. The elevated levels of lysine, saccharopine, and α-aminoadipic acid found in LY038 are expected to be readily degraded upon consumption as occurs with existing sources of lysine in the diet, without any accumulation or adverse effects. At the expected level of consumption, there was no greater concern with corn lines containing event LY038 than non-transgenic corn, with respect to its potential for toxicity or allergenicity.
Health Canada's review of the information presented in support of the food use of corn lines containing event LY038 concluded that the food use of corn lines containing this event does not raise concerns related to safety. Health Canada is of the opinion that LY038 is similar to non-transgenic parental strains of corn in terms of being an acceptable food source.
Health Canada's opinion deals only with the human food use of corn lines containing event LY038. Issues related to its use as livestock feed have been addressed separately through existing regulatory processes in the Canadian Food Inspection Agency.
This Novel Food Information document has been prepared to summarize the opinion regarding the subject product provided by the Food Directorate, Health Products and Food Branch, Health Canada. This opinion is based upon the comprehensive review of information submitted by the petitioner according to the Guidelines for the Safety Assessment of Novel Foods.
For further information, please contact:
Novel Foods Section
Food Directorate Telephone: (613) 941-5535
Health Products and Food Branch Facsimile: (613) 952-6400
Health Canada, PL2204A1
251 Frederick Banting Driveway
Ottawa, Ontario K1A 0K9
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