|Legaspi, JR., Benjamin - TEXAS A&M UNIVERSITY|
|Bernal, Julio - TEXAS A&M UNIVERSITY|
|Setamou, Mamoudou - TEXAS A&M UNIVERSITY|
Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: November 1, 2003
Publication Date: February 1, 2004
Citation: Legaspi, J.C., Legaspi, Jr., B.C., Bernal, J., Setamou, M. 2004. Insect resistant transgenic crops expressing plant lectins. In Transgenic Crop Protection: Concepts and Strategies. Opender, Koul, and G.S. Dhaliwal, eds. Science Publishers, Inc. USA. 85-116. Interpretive Summary: The use of genetically-engineered or transgenic crops for insect resistance is increasing worldwide. Transgenic crops are those that have been transformed by incorporating a resistant gene; for example, plant lectins or insecticidal proteins. This tactic of introducing resistant genes in economically important crops such as rice, wheat, potato and sugarcane will play a major role in development of integrated pest management. For example, sugarcane was genetically engineered to produce a substance that is toxic to many insect pests. This gene, Galanthus nivalis agglutinin (GNA), was transferred from the snowdrop lily into sugarcane. The gene causes sugarcane to produce a protein called a lectin in all parts of the plant. The lectin interferes with insect digestion, although numerous tests have shown no ill effects against mammals and birds. Laboratory, greenhouse and field studies have shown deleterious effects of transgenic sugarcane against a major insect pest, the Mexican rice borer, Eoreuma loftini. Further laboratory and field studies to date have shown no adverse effects of transgenic sugarcane on non-target insects such as the parasites of the stalkborers. These studies suggest that use of transgenic crops and biological control tactics may be compatible in an integrated pest management program.
Technical Abstract: Transgenic insecticidal crop cultivars are revolutionizing agriculture and will likely become a major insect management tactic worldwide. Insect resistant crops can be developed by introducing novel resistance genes into economically important crops. The tactic has a potentially key role in integrated pest management of several important pests. In this chapter, we discuss transfer of genes expressing secondary plant compounds called lectins into crops of agricultural significance. This focus is primarily on Galanthus nivalis agglutinin (GNA) from the snowdrop lily, because it is an especially promising lectin with much research interest. Lectins are a large, heterogenous family of carbohydrate-binding proteins. Plant lectins, especially those in seeds, may play a role in defense against attack by bacteria, fungi and predation by animals and insects. The precise mechanism of action of insecticidal lectins is unknown. However, binding to specific carbohydrates and agglutination in the insect midgut has been clearly demonstrated. Insecticidal activity of lectins can be measured in two general ways: 1) purified lectin or extracts from transformed plant material is applied topically or incorporated into artificial diets and presented to target insects; and 2) whole plants or excised sections of plants may be presented to insects, i.e., in planta methods, to evaluate transgenic plant lines for insect resistance. Results of studies on efficacy of GNA-transgenic lectin crops such as tobacco, potato, sugarcane, and rice against major insect pests will be presented. Effects of transgenic crops on nontarget insects will also be discussed. Based on the studies to date, transgenic crops have much potential to contribute to the development of integrated pest management strategies for crops.