Toxicity of lectins and processing of ingested proteins in the pea aphid Acyrthosiphon pisum

Abstract

Acute toxicity of thirty lectins was tested against the pea aphid Acyrthosiphon pisum (Harris) (Homoptera, Aphididae: Macrosiphini). Activity was measured on artificial diets containing moderate concentrations of lectins (10–250 μg/ml) by scoring mortality and growth inhibition over the whole nymphal period (7 days at 20°C). Most of the proteins tested exhibited low toxicity, but some induced significant mortality; these included the lectins from jackbean (Concanavalin A), amaranth, lentil and snowdrop. There was no direct correlation between toxicity and sugar specificity of the lectin; however, many mannose‐binding lectins were toxic towards A. pisum. Concanavalin A was also tested on five other aphid species (Aphis gossypii, Aulacortum solani, Macrosiphum euphorbiae, Macrosiphum albifrons and Myzus persicae) at concentrations between 10–1500 μg/ml. Mortality was very variable from one species to another. Strong growth inhibition invariably occurred within this concentration range, although dose‐response curves differed substantially between aphid species. The peptidase complement of A. pisum's digestive tract was also investigated, as well as the oral toxicity of some protease inhibitors (PIs) to this aphid. Most protein PIs were inactive, and no part of the digestive tract contained detectable amounts of endo‐protease activity. This is in contrast to the strong amino‐peptidase activity which was shown to occur predominantly in the midgut and crop portions of the digestive tract. The potential of lectins in transgenic crops to confer Host‐Plant Resistance to aphids is discussed.

Functional Characterization of HFR1, a High-MannoseN-Glycan-Specific Wheat Lectin Induced by Hessian Fly Larvae

“…The snowdrop lectin, GNA, is toxic to brown planthopper (Nilaparvata lugens; Powell et al, 1998;Tang et al, 2001) and tomato moth (Lacanobia oleracea) larvae (Fitches et al, 1997;Gatehouse et al, 1997Gatehouse et al, , 1999 as well as to several aphid species (Hilder et al, 1995;Rahbé et al, 1995;Gatehouse et al, 1996;Sauvion et al, 1996). Concanavalin A (lectin from Canavalia ensiformis) shows significant antimetabolic activity toward third-instar nymphs of taro planthopper (Tarophagous proserpina; Powell, 2001).…”

Plant‐insect interactions: what can we learn from plant lectins?

“…Another plant lectin with a high toxicity level towards A. pisum was the mannose/ glucose-specific jackbean lectin ConA (Rahbé et al, 1995). Increased mortality and negative effects on growth and development were also noted in other species, both lepidopteran and hemipteran (Fitches et al, 2001;Gatehouse et al, 1999;Sauvion et al, 1996).…”

“…The galactose-specific Amaranthus caudatus lectin (ACA) was shown to be highly toxic towards the pea aphid A. pisum (Rahbé et al, 1995). Using transgenic cotton plants expressing the Amaranthus lectin, Wu et al (2006) noted an inhibition of population growth of the cotton aphid Aphis gossypii.…”

“…Screenings of a wide range of lectins demonstrated that the Galanthus nivalis agglutinin (GNA) has the highest anti-insect potential (Rahbé et al, 1995). Subsequently, the effects of other GNA-related lectins were also investigated.…”

“…Although Rahbé et al (1995) did not record any significant level of toxicity by wheat germ agglutinin (WGA) towards A. pisum, this lectin was shown to exert negative effects on the American bollworm Helicoverpa armigera, the mustard aphid L. erysimi, and the rice brown planthopper N. lugens (Gupta et al, 2005;Kanrar et al, 2002;Powell et al, 1995a). Indeed, lectins with N-acetylglucosamine-specificity have a high affinity for chitin, the main constituent of the peritrophic matrix in the insect gut (Hakim et al, 2010).…”