Entomotoxic action of jackbean lectin (Con A) in bird cherry-oat aphid through the effect on insect enzymes

Abstract

The mechanism of the toxicity of plant lectins is not clearly understood. The insecticidal activity of plant lectins results from effects on insect metabolism by interfering with gut enzymatic function. Thus, a greater understanding of the mechanisms of plant lectin toxicity in insects is required. This study reports the effects of dietary ingestion of the glucose-mannose binding lectin Concanavaline A (Con A) on bird cherry-oat aphid (Rhopalosiphum padi L.) enzymes involved in protein digestion [aminopeptidase N and cathepsin L (CatL)], sugar (α- and β-glucosidases), and phosphorus (alkaline and acid phosphatase) metabolism. An aphid bioassay test using artificial diets containing Con A is also presented. An increase in the concentration of Con A generally suppressed the activity of glucosidases and phosphatases, and increased the activity of CatL in apterae morphs. Bird cherry-oat aphid performance was affected by the presence of Con A in artificial diets. The lectin added to the liquid diet increased the pre-reproductive period, mortality, and the average time of generation development (T) and decreased fecundity and the intrinsic rate of natural increase (rm). Aphicidal activity of Con A might be linked to its interference in the activity of digestive enzymes.