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Unintended Effects of Genetic Manipulation
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Sugarcane plants with lectin transgene for stemborer resistance showed altered growth.

Manipulated Organism: Sugarcane (Saccharum sp.), cultivar CP65-357, line 83.

Inserted Transgenes: Mannose-binding lectin gene for the production of the protein GNA (snowdrop lectin), derived from the snowdrop (Galanthus nivalis). The gene was fused to the maize ubiquitin promoter so that the gene would be expressed in all parts of the plant.

Goal: Create transgenic sugarcane that produces snowdrop lectin (GNA) in all its tissues. GNA is toxic to a variety of insect larvae, including the stemborer Eoreuma loftini, which is the principle pest of sugarcane in south Texas. Over goal is to improve control of the stemborer Eoreuma loftini.

Intended Effect: Transgenic sugarcane does produce snowdrop lectin and is toxic to Eoreuma loftini.

Unintended Effects: In greenhouse experiments, adult moths of the stemborer laid significantly fewer eggs and fewer egg masses on transgenic sugarcane than on unmanipulated control plants. This was, in the authors' view, related to morphological differences between the transgenic sugarcane plants and unmanipulated controls. At three months the transgenic plants
  • were significantly shorter than controls (with an average height of 127 cm, they were on average 41 cm shorter than controls);
  • had two to three fewer leaves overall, including fewer drier leaves.
The moths laid more eggs on the controls with their greater height and more dry leaves.

Additional Comments: The authors conclude: "Although this unintentional effect of transgenic sugarcane is positive in the context of pest management, it underscores the validity of concerns over unanticipated consequences of releasing transgenic organisms" (p. 892).

Source: Bernal, J. S. and M. Sëtamou (2003). "Fortuitous Antixenosis in Transgenic Sugarcane: Antibiosis-Expressing Cultivar is Refractory to Ovipositing Herbivore Pests," Environmental Entomology vol. 32, pp. 886-94.

Author Affiliations: Biological Control Laboratory, Texas A & M University.

Funding: Rio Grande Valley Sugar Growers.

Product Status: Not on the market as of 2008.

Copyright 2008 The Nature Institute.

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