Mechanisms of the insecticidal action of TEL (Talisia esculenta lectin) against Callosobruchus maculatus (Coleoptera: Bruchidae).
Plant lectins have insecticidal activity that is probably mediated through their ability to bind carbohydrates. To examine the influence of sugars on the insecticidal activity of a lectin from Talisia esculenta seeds (TEL), the lectin was mixed with mannose, glucose, or mannose plus glucose. Mannose abolished the insecticidal activity. Affinity chromatography showed that TEL bound to midgut proteins of the insect Callosobruchus maculatus. Immunoblotting showed that TEL recognized some proteins, probably glycoproteins, present in the midgut membrane of this insect. The principal proteases responsible for digestive proteolysis in fourth instar larvae of C. maculatus were purified by chromatography on activated thiol-Sepharose. These purified proteases were unable to digest TEL after a 15-h incubation. These results suggest that the insecticidal activity of TEL involves a specific carbohydrate-lectin interaction with glycoconjugates on the surface of digestive tract epithelial cells, as well as binding to assimilatory glycoproteins present in midgut extracts and resistance to enzymatic digestion by cysteine proteinases.
Macedo
Maria Lígia Rodrigues
ML
Laboratório de Purificação de Proteínas e suas Funções Biológicas, Departamento de Ciências Naturais, Universidade Federal de Mato Grosso do Sul, Três Lagoas, MS, Brazil.
de Castro
Márcia Mota
MM
Freire
Maria das Graças Machado
Md
D000818:Animals; D001681:Biological Assay / Q000379:methods; D001835:Body Weight; D002241:Carbohydrates / Q000494:pharmacology; D001517:Coleoptera / Q000187:drug effects* / Q000201:enzymology; D003546:Cysteine Endopeptidases / Q000378:metabolism; D004064:Digestive System / Q000201:enzymology; D007306:Insecticides / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology*; D007413:Intestinal Mucosa / Q000378:metabolism; D007814:Larva / Q000187:drug effects; D037121:Plant Lectins / Q000037:antagonists & inhibitors / Q000378:metabolism / Q000494:pharmacology*; D029631:Sapindaceae / Q000737:chemistry*; D012639:Seeds / Q000737:chemistry; D016019:Survival Analysis
D002241:Carbohydrates; D007306:Insecticides; D037121:Plant Lectins; D003546:Cysteine Endopeptidases