Toxicity of Hydrolyzed Vicilins toward Callosobruchus maculatus and Phytopathogenic Fungi

Abstract

Studies have shown that vicilins (7S storage proteins) from seeds were able to bind to the surface of the Callosobruchus maculatus larval midgut and to the peritrophic matrices of the midguts of Diatraea saccharalis and Tenebrio molitor , inhibiting larval development. Vicilins were also shown to inhibit yeast growth and bind to yeast cells through the association with chitin-containing structures. The present work studies the association of peptides from vicilins of genotypes of Vigna unguiculata (susceptible and resistant to bruchid) with acetylated chitin and the toxicity of vicilin fragments and chitin-binding vicilin fragments to C. maculatus and phytopathogenic fungi. Hydrolysis of vicilins with alpha-chymotrypsin results in a complex mixture of fragments that were separated by chitin-affinity chromatography. Chitin-binding peptides from both genotypes were toxic to C. maculatus larvae, and alpha-chymotrypsin-hydrolyzed vicilins were deleterious to the above insect and to Fusarium oxysporum , Colletotrichum musae , and Saccharomyces cerevisiae fungi.

Vicilin from Anadenanthera colubrina Seeds: An alternative tool to combat Callosobruchus maculatus

“…The fragments of the digestion of the AcV in vitro, which were between 10 and 30 kDa, corroborate results obtained for vicilin from V. unguiculata - IT81D 1045 Cultivar ( Sales et al, 1992 ) and Albizia Lebbeck ( Souza et al, 2012 ). Similar to that found by Uchôa et al, 2009 , Oliveira et al, 2014 , AcV maintained its ability to connect the chitin matrix, giving indications of its toxicity. These portions, which remain integrated with the ability to bind to the peritrophic matrix of the average gut of larvae, prevent the absorption of food and promote death due to the low nutrition of C. Maculatus .…”

Identification of Albizia lebbeck seed coat chitin-binding vicilins (7S globulins) with high toxicity to the larvae of the bruchid Callosobruchus maculatus

“…A. lebbeck seed coat flour was shown to be toxic to the larvae, causing considerable lethality and weight loss of 20-day-old larvae. After several purification steps, we obtained a highly toxic vicilin-rich sample that was subsequently shown to have strong chitin-binding activity, with consequent toxicity of certain vicilins to chitin-containing structures in the insect midgut epithelium and fungal cell walls (5,8,12-14,33). It has been hypothesized that particular plant chitin-binding proteins can adhere to insect PMs, interfering with their normal functions and affecting nutrient absorption (12).…”

“…After several purification steps, we obtained a highly toxic vicilin-rich sample that was subsequently shown to have strong chitin-binding activity, with consequent toxicity of certain vicilins to chitin-containing structures in the insect midgut epithelium and fungal cell walls (5,8,12-14,33). It has been hypothesized that particular plant chitin-binding proteins can adhere to insect PMs, interfering with their normal functions and affecting nutrient absorption (12). In addition, chitin-binding vicilins from several plants have been demonstrated to be toxic to several species of insects and fungi (5,8,13,14,34).…”

“…In addition to their major role as energy source, alternative functions for vicilins have been proposed in sucrose binding (3), desiccation (4) and defense against insects and fungi (5-8). Several cotyledonary and tegumental vicilins can confer protection against Callosobruchus maculatus (9-12), the sugarcane borer Diatraea saccharalis (13) and Tenebrio molitor (8) larvae. In addition, vicilins isolated from various legume seeds (e.g., Vigna angularis , Phaseolus vulgaris and Glycine max ) also impaired C. maculatus larval development (14).…”

“…In addition, vicilins isolated from various legume seeds (e.g., Vigna angularis , Phaseolus vulgaris and Glycine max ) also impaired C. maculatus larval development (14). Furthermore, the mechanism of vicilin toxicity to some insects has been associated with their chitin-binding properties (5,6,12-14). Chitin is an extracellular amino-sugar polymer of N-acetyl-ß-glucosamine that is an essential structural component of fungal cell walls, exoskeletons and peritrophic membranes (PM; in arthropods) (15).…”