Modulation of a Lectin Insecticidal Acitivity by Carbohydrates

摘要

Lectins from plants present an insecticidal activity most prob- ably through their carbohydrate binding properties; as a conse- quence, their toxicity should vary with the presence of a competitive sugar in the ingested food. In order to test this hy- pothesis, we performed competition experiments between insec- ticidal activity and carbohydrate binding. For this purpose, we used a lectin from Lathyrus ochrus and the specific carbohydrate for this protein, glucose. In toxicological tests with Drosophila melanogaster, we observed a decrease of lectin toxicity when glu- cose was added to the larva-rearing medium. This result suggests that the toxicity of the lectin is correlated to its ability to bind sugar in the insect digestive tract and stresses the importance of sugar composition of the nutriment used for toxicological test- ing of lectins or in genetically modified plants.