title: Toxicity and Binding Studies of Bacillus thuringiensis Cry1Ac, Cry1F, Cry1C, and Cry2A Proteins in the Soybean Pests Anticarsia gemmatalis and Chrysodeixis (Pseudoplusia) includens.
abstract: Anticarsia gemmatalis(velvetbean caterpillar) andChrysodeixis includens(soybean looper, formerly namedPseudoplusia includens) are two important defoliating insects of soybeans. Both lepidopteran pests are controlled mainly with synthetic insecticides. Alternative control strategies, such as biopesticides based on theBacillus thuringiensis(Bt) toxins or transgenic plants expressing Bt toxins, can be used and are increasingly being adopted. Studies on the insect susceptibilities and modes of action of the different Bt toxins are crucial to determine management strategies to control the pests and to delay outbreaks of insect resistance. In the present study, the susceptibilities of both soybean pests to the Bt toxins Cry1Ac, Cry1Fa, Cry1Ca, and Cry2Aa have been investigated. Bioassays performed in first-instar larvae showed that both insects are susceptible to all these toxins. Competition-binding studies carried out with Cry1Ac and Cry1Fa125-iodine labeled proteins demonstrated the presence of specific binding sites for both of them on the midgut brush border membrane vesicles (BBMVs) of bothA. gemmatalisandC. includensCompetition-binding experiments and specific-binding inhibition studies performed with selected sugars and lectins indicated that Cry1Ac and Cry1Fa share some, but not all, binding sites in the midguts of both insects. Also, the Cry1Ac- or Cry1Fa-binding sites were not shared with Cry1Ca or Cry2Aa in either soybean pest. This study contributes to the knowledge of Bt toxicity and midgut toxin binding sites inA. gemmatalisandC. includensand sheds light on the cross-resistance potential of Cry1Ac, Cry1Fa, Cry1Ca, and Cry2Aa Bt proteins as candidate proteins for Bt-pyramided crops.IMPORTANCEIn the present study, the toxicity and the mode of action of theBacillus thuringiensis(Bt) toxins Cry1Ac, Cry1Fa, Cry1Ca, and Cry2Aa inAnticarsia gemmatalisandChrysodeixis includens(important defoliating pests of soybeans) have been investigated. These studies are crucial for determining management strategies for pest control. Bioassays showed that both insects were susceptible to the toxins. Competition-binding studies demonstrated the presence of Cry1Fa- and Cry1Ac-specific binding sites in the midguts of both pests. These results, together with the results from binding inhibition studies performed with sugars and lectins, indicated that Cry1Ac and Cry1Fa share some, but not all, binding sites, and that they were not shared with Cry1Ca or Cry2Aa in either soybean pest. This study contributes to the knowledge of Bt toxicity inA. gemmatalisandC. includensand sheds light on the cross-resistance potential of Cry1Ac, Cry1Fa, Cry1Ca, and Cry2Aa Bt proteins as candidate proteins for Bt-pyramided crops.
authors.affiliation: Department of Genetics, Universitat de València, Burjassot, Spain.|Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BioTecMed), Universitat de València, Burjassot, Spain.
authors.forename: Yolanda
authors.initials: Y
authors.lastname: Bel
authors.affiliation: Dow AgroSciences, Indianapolis, Indiana, USA.
authors.forename: Joel J
authors.initials: JJ
authors.lastname: Sheets
authors.affiliation: Dow AgroSciences, Indianapolis, Indiana, USA.
authors.forename: Sek Yee
authors.initials: SY
authors.lastname: Tan
authors.affiliation: Dow AgroSciences, Indianapolis, Indiana, USA.
authors.forename: Kenneth E
authors.initials: KE
authors.lastname: Narva
authors.affiliation: Department of Genetics, Universitat de València, Burjassot, Spain baltasar.escriche@uv.es.|Estructura de Recerca Interdisciplinar en Biotecnologia i Biomedicina (ERI BioTecMed), Universitat de València, Burjassot, Spain.
authors.forename: Baltasar
authors.identifier: http://orcid.org/0000-0003-4889-793X
authors.initials: B
authors.lastname: Escriche
mesh_terms: D000818:Animals; D001413:Bacillus thuringiensis / Q000737:chemistry; D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins / Q000633:toxicity*; D004731:Endotoxins / Q000633:toxicity*; D006460:Hemolysin Proteins / Q000633:toxicity*; D007814:Larva / Q000187:drug effects / Q000502:physiology; D009036:Moths / Q000187:drug effects* / Q000502:physiology; D010572:Pest Control, Biological; D010935:Plant Diseases / Q000469:parasitology* / Q000517:prevention & control; D013025:Glycine max / Q000469:parasitology*
chemical_list: D000083722:Bacillus thuringiensis Toxins; D001426:Bacterial Proteins; D004731:Endotoxins; D006460:Hemolysin Proteins; C030956:insecticidal crystal protein, Bacillus Thuringiensis
keywords: Cry proteins; heterologous competition; soya pest; soybean looper; velvetbean caterpillar