Cadherin Protein Is Involved in the Action of Bacillus thuringiensis Cry1Ac Toxin in Ostrinia furnacalis

Abstract

Transgenic crops expressing Bacillus thuringiensis (Bt) insecticidal proteins have been extensively planted for insect pest control, but the evolution of Bt resistance in target pests threatens the sustainability of this approach. Mutations of cadherin in the midgut brush border membrane was associated with Cry1Ac resistance in several lepidoptera species, including the Asian corn borer, Ostrinia furnacalis, a major pest of maize in Asian–Western Pacific countries. However, the causality of O. furnacalis cadherin (OfCad) with Cry1Ac resistance remains to be clarified. In this study, in vitro and in vivo approaches were employed to examine the involvement of OfCad in mediating Cry1Ac toxicity. Sf9 cells transfected with OfCad showed significant immunofluorescent binding with Cry1Ac toxin and exhibited a concentration-dependent mortality effect when exposed to Cry1Ac. The OfCad knockout strain OfCad-KO, bearing homozygous 15.4 kb deletion of the OfCad gene generated by CRISPR/Cas9 mutagenesis, exhibited moderate-level resistance to Cry1Ac (14-fold) and low-level resistance to Cry1Aa (4.6-fold), but no significant changes in susceptibility to Cry1Ab and Cry1Fa, compared with the original NJ-S strain. The Cry1Ac resistance phenotype was inherited as autosomal, recessive mode, and significantly linked with the OfCad knockout in the OfCad-KO strain. These results demonstrate that the OfCad protein is a functional receptor for Cry1Ac, and disruption of OfCad confers a moderate Cry1Ac resistance in O. furnacalis. This study provides new insights into the mode of action of the Cry1Ac toxin and useful information for designing resistance monitoring and management strategies for O. furnacalis.

Alteration of a Cry1A Shared Binding Site in a Cry1Ab-Selected Colony of Ostrinia furnacalis

“…A later study characterized the alteration of aminopeptidase N and ABC type G transcripts in both the ACB-AbR colony (studied here) and the ACB-AcR colony [21]. Recently, the involvement of the O. furnacalis cadherin in the toxicity of Cry1Aa and Cry1Ac was proven through CRISPR knock-outs [22], as well as the ABCC2 in the toxicity of Cry1F and Cry1Ab/c [23]. The binding sites here proposed could be located in some of these receptors or even in different epitopes of the same one, as has been shown for Cry1A proteins and the ABCC2 transporter in Spodoptera exigua [24,25].…”

Performance insights into spray-dryer microencapsulated Bacillus thuringiensis cry pesticidal proteins with gum arabic and maltodextrin for effective pest control

“…Several studies in the literature have reported that Cry toxin receptors are located in BBM, including cadherin-like (Aimanova et al 2006 ; Zhang et al 2020 ; Jin et al 2021 ), aminopeptidase N (APN) (Wei et al 2016 ; Shao et al 2018 ), and alkaline phosphatase (ALP) (Likitvivatanavong et al 2011 ; Stalinski et al 2016 ). The activated toxin samples from the different formulated products analyzed in this work showed similar binding to BBMV from two lepidopteran insects.…”

CRISPR-Cas9 knockout of membrane-bound alkaline phosphatase or cadherin does not confer resistance to Cry toxins in Aedes aegypti

“…Here, we were persistent to generate the Aae-Cad KO in A . aegypti , since previous works have successfully generated the Cad KO mutations in lepidopteran species using CRISPR-Cas9 technology and the role of this protein as a functional receptor for Cry toxins has been demonstrated [ 24 , 25 , 27 , 28 ]. Our CRISPR-Cas9 KO mutations in the aae-cad gene resulted in the generation of premature stop codons in the mRNA.…”