Variant vicilins from a resistant Vigna unguiculata lineage (IT81D-1053) accumulate inside Callosobruchus maculatus larval midgut epithelium.
It has been demonstrated that variant vicilins are the main resistance factor of cowpea seeds (Vigna unguiculata) against attack by the cowpea beetle Callosobruchus maculatus. There is evidence that the toxic properties of these storage proteins may be related to their interaction with glycoproteins and other microvillar membrane constituents along the digestive tract of the larvae. New findings have shown that following interaction with the microvilli, the vicilins are absorbed across the intestinal epithelium and thus reach the internal environment of the larvae. In the present paper we studied the insecticidal activity of the variant vicilins purified from a resistant cowpea variety (IT81D-1053). Bioassays showed that the seeds of this genotype affected larval growth, causing developmental retardation and 100% mortality. By feeding C. maculatus larvae on susceptible and IT81D-1053 derived vicilins (FITC labelled or unlabelled), followed by fluorescence and immunogold cytolocalization, we were able to demonstrate that both susceptible and variant forms are internalized in the midgut cells and migrate inside vesicular structures from the apex to the basal portion of the enterocytes. However, when larvae were fed with the labelled vicilins for 24h and then returned to a control diet, the concentration of the variant form remained relatively high, suggesting that variant vicilins are not removed from the cells at the same rate as the non-variant vicilins. We suggest that the toxic effects of variant vicilins on midgut cells involve the binding of these proteins to the cell surface followed by internalization and interference with the normal physiology of the enterocytes, thereby affecting larval development in vivo.
Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, C.P. 476, 88040-900, Florianópolis, SC, Brazil.
Gabriel B
GB
Oliveira
Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, C.P. 476, 88040-900, Florianópolis, SC, Brazil.
Daniele
D
Kunz
Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, C.P. 476, 88040-900, Florianópolis, SC, Brazil.
Tanara V
TV
Peres
Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, C.P. 476, 88040-900, Florianópolis, SC, Brazil.
Rodrigo B
RB
Leal
Departamento de Biologia Celular e Genética, Centro de Biociências, Universidade Federal do Rio Grande do Norte, 59072-970, Natal, RN, Brazil.
Adriana F
AF
Uchôa
Laboratório de Entomologia e Fitopatologia, Centro de Ciências e Tecnologia Agropecuárias, Universidade Estadual do Norte Fluminense Darcy Ribeiro, 28013-602, Campos dos Goytacazes, RJ, Brazil.
Richard I
RI
Samuels
Departamento de Tecnologia de Alimentos e Saúde Pública, Universidade Federal de Mato Grosso do Sul, C.P. 549, 79070-900, Campo Grande, MS, Brazil.
Maria Lígia R
ML
Macedo
Departamento de Biofísica e Centro de Biotecnologia, Instituto de Biociências, Universidade Federal do Rio Grande do Sul, 91501-970, Porto Alegre, RS, Brazil.
Célia R
CR
Carlini
Departamento de Genética e Biologia Evolutiva, Instituto de Biociências, Universidade de São Paulo, C.P. 11461, 05422-970, São Paulo, SP, Brazil.
Alberto F
AF
Ribeiro
Departamento de Biologia, Centro de Ciências, Universidade Federal do Ceará, 60455-970, Fortaleza, CE, Brazil.
Thalles B
TB
Grangeiro
Departamento de Bioquímica, Instituto de Química, Universidade de São Paulo, C.P. 26077, 05513-970, São Paulo, SP, Brazil.
Walter R
WR
Terra
Laboratório de Química e Função de Proteínas e Peptídeos, Centro de Biociências e Biotecnologia, Universidade Estadual do Norte Fluminense Darcy Ribeiro, 28013-600, Campos dos Goytacazes, RJ, Brazil.
José
J
Xavier-Filho
Departamento de Bioquímica, Centro de Ciências Biológicas, Universidade Federal de Santa Catarina, C.P. 476, 88040-900, Florianópolis, SC, Brazil. Electronic address: capsilva@ccb.ufsc.br.
Carlos P
CP
Silva
D000818:Animals; D001517:Coleoptera / Q000378:metabolism*; D004064:Digestive System / Q000378:metabolism; D060467:Disease Resistance; D004848:Epithelium / Q000378:metabolism; D007887:Fabaceae / Q000378:metabolism*; D007814:Larva / Q000254:growth & development / Q000378:metabolism; D008871:Microvilli / Q000378:metabolism; D010572:Pest Control, Biological; D055314:Seed Storage Proteins / Q000378:metabolism*; D012639:Seeds / Q000378:metabolism*
D055314:Seed Storage Proteins; C015575:vicilin protein, plant
Antibiosis; Endocytosis; Insect midgut; Protein absorption; Vicilin