Silencing of an ABC transporter, but not a cadherin, decreases the susceptibility of Colorado potato beetle larvae to Bacillus thuringiensis ssp. tenebrionis Cry3Aa toxin

Abstract

The Colorado potato beetle, Leptinotarsa decemlineata (Coleoptera: Chrysomelidae), is a major pest of potato plants worldwide and is notorious for its ability to develop resistance to insecticides. Cry3 toxins synthesized by Bacillus thuringiensis ssp. tenebrionis have been used successfully to manage this pest. Resistance to Cry toxins is a concerning problem for many insect pests; therefore, it is important to determine the mechanisms by which insects acquire resistance to these toxins. Cadherin‐like and ABC transporter proteins have been implicated in the mode of action of Cry toxins as mutations in these genes render lepidopterans resistant to them; however, clear consensus does not exist on whether these proteins also play a role in Cry3 toxin activity and/or development of resistance in coleopterans. In the current study, we identified the L. decemlineata orthologues of the cadherin (LdCAD) and the ABCB transporter (LdABCB1) that have been implicated in the mode of action of Cry toxins in other coleopterans. Suppression of LdABCB1 via RNA interference reduced toxin‐related larval mortality, whereas partial silencing of LdCAD did not. Our results suggest that the ABCB is involved in the mode of action of Cry3Aa toxins; however, no evidence was found to support the role of cadherin as a receptor of Cry3Aa in L. decemlineata.

Interactions between evolved pesticide resistance and pesticide exposure influence immunity against pathogens

“…Interestingly, single exposure to OP or Btt induced downregulation of an ABC transporter but this transcript was upregulated with co-exposure to OP and Btt . ABC transporters have been identified as receptors for Bt Cry proteins and aid in membrane pore formation (Güney et al, 2021; Heckel, 2021; Pauchet et al, 2016), and the additional function of ABC transporters as xenobiotic pumps may help to mediate Bt toxicity (Dermauw & Leeuwen, 2014; Wu et al, 2019). It is also possible that OP and Btt interact directly, as would be the case if Btt actively degrades OP for energy (Kumar et al, 2018) or if OP facilitates Btt germination rates.…”

Leveraging RNA Interference to Impact Insecticide Resistance in the Colorado Potato Beetle, Leptinotarsa decemlineata

“…Although knockdown of these targets did not lead to an increase in ivermectin susceptibility, assessing the impact of reducing the endogenous levels of these transporters in insects resistant to other compounds, nevertheless, remains of interest to further understand their role, if any, in insecticide response. It is interesting to point out that RNAi-based modulation of LdABCB1 transcript levels was also linked to a reduction in Cry3Aa toxin-mediated toxicity in L. decemlineata larvae [ 53 ]. Select studies that have highlighted the importance of ABC transporters for insecticide resistance in L. decemlineata are presented in Table 3 .…”

Molecular and Kinetic Models for Pore Formation of Bacillus thuringiensis Cry Toxin

“…CRISPR/Cas9-mediated cadherin knockout in H. armigera caused Cry1Ac resistance but no significant change in Cry2Ab susceptibility [ 49 ]. Cadherin silencing did not decrease Cry3Aa susceptibility in Diabrotica virgifera [ 50 ] and Cry3B susceptibility in Leptinotarsa decemlineata [ 51 ]. Cadherin, sometimes, does not even mediate Cry1A toxicity.…”