ARCHIVED - Novel Hybridization System For Corn (MS3)

FD/OFB-97-10
November, 1997

Novel Food Information - Food Biotechnology

Health Canada has notified Plant Genetics Systems (Canada) Inc. that it has no objection to the food use of corn derived from a new hybridization system based on male sterility (MS3), developed using genetic modification. The Department conducted a comprehensive assessment of the MS3 system according to its Guidelines for the Safety Assessment of Novel Foods (September, 1994). These guidelines are based upon internationally accepted principles for establishing the safety of foods derived from genetically modified organisms.

BACKGROUND:

The following provides a summary regarding the Plant Genetics Systems (Canada) Inc. notification to Health Canada and contains no confidential business information.

1. Introduction

A novel hybridization system for corn (Zea mays) has been developed by Plant Genetic Systems N.V. This system involves the use of a line which is male sterile and therefore does not produce pollen. Crossing the male sterile plants with a fertile line results in hybrid plants which are known to produce higher yields than conventional varieties. Linked to this hybridization system is tolerance to the non-selective herbicide glufosinate ammonium, the active ingredient in Liberty® herbicide, which facilitates the maintenance of the male sterile, female parent line.

2. Development of the Modified Plant

The MS3 transformant was produced by transforming a corn cultivar to introduce DNA containing the barnase gene isolated from the common soil bacterium Bacillus amyloliquefaciens and the bar gene isolated from the common soil microorganism Streptomyces hygroscopicus.

The introduced barnase gene encodes a ribonuclease (RNAse) enzyme and is linked to an anther-specific promoter which directs expression of the gene to the anther of the plant flower where pollen is produced. The introduced bar gene codes for the enzyme phosphinothricin acetyl transferase (PAT). The introduced DNA further includes the barstar gene from B. amyloliquefaciens which encodes a specific inhibitor of the RNAse enzyme encoded by the introduced barnase gene. The barstar gene is under the control of bacterial expression signals and is therefore not functional in plants, but is necessary to prevent the RNAse from disrupting the development of bacteria in which the introduced DNA was prepared. Also included on the introduced DNA is the bla and cat genes under the control of bacterial expression signals. These genes encode resistance to the antibiotics ampicillin and chloramphenicol, respectively, and were included as selectable markers for the development of the introduced DNA in bacteria. Neither of these selectable marker genes is functional in plants.

3. Product Information

Expression of the introduced barnase gene in MS3 corn plants results in the expression of the RNAse enzyme which disrupts cell development by affecting cellular RNA. When expressed in the anther as directed by the specific promoter, this enzyme disrupts pollen development. The inhibition of the pollen development means that the plant is rendered male sterile, but retains the female parts of the flowers. The expressed PAT enzyme, resulting from the introduced bar gene, mediates the rapid metabolism of glufosinate ammonium, permitting the plants to tolerate application of the herbicide. The introduced genes have been sequenced and their functions are well characterized. Detailed molecular analyses demonstrated that the expression of the introduced genes is limited to the leaves and flowers of the plants with no expression being detectable in the seeds.

MS3 corn differs from non-transgenic corn only in the insertion of five new genes, barnase, barstar, bar, bla and cat and in the expression of two new proteins, RNAse, and PAT. As noted, the barstar, bla and cat genes are non-functional in plants and therefore do not produce proteins.

4. Dietary Exposure

Grain from hybrids derived from MS3 corn is primarily intended for animal feeding. However, such field corn may be dry- or wet-milled into various processed corn products for human food use. The human food uses of such grain is not expected to be different from the uses of non-transgenic field corn varieties. As such, the dietary exposure of Canadians to grain from MS3-derived corn hybrids will not be different from that for other commercially available field corn varieties. Furthermore, since neither of the introduced proteins are detected in the corn grain, there would be no dietary exposure to these introduced proteins.

5. Nutrition

The composition of grain from MS3-derived hybrid corn was compared to grain from nontransgenic corn. Parameters such as moisture, fibre, fat protein, ash, starch, oil, fatty acids and the amino acid composition were compared with no significant differences being observed.

The use of grain from MS3-derived corn hybrids would therefore have no significant impact on the nutritional quality of the Canadian food supply.

CONCLUSION:

Health Canada's review of the information presented in support of the food use of grain from the novel hybridization system for corn based on male sterility (MS3) concluded that this grain does not raise concerns related to safety. Health Canada is of the opinion that grain from MS3-derived hybrid corn is as safe and nutritious as grain from current commercial corn varieties. Health Canada's opinion deals only with the food use of grain from the novel hybridization system for corn based on male sterility (MS3). Issues related to growing MS3, and MS3-derived hybrids in Canada and their use as animal 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 Protection 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:

Office of Food Biotechnology
Food Directorate
Health Protection Branch
Health Canada
Tunney's Pasture
Ottawa, Ontario K1A 0L2
Telephone: (613) 952-5137
Facsimile: (613) 952-6400