Inhibitor of apoptosis is an effective target gene for RNAi‐mediated control of Colorado potato beetle,Leptinotarsa decemlineata

Abstract

The Colorado potato beetle (CPB; Leptinotarsa decemlineata) is one of the most notorious and difficult to control pests of potato and other solanaceous crops in North America. This insect has evolved a remarkable ability to detoxify both plant and synthetic toxins, allowing it to feed on solanaceous plants containing toxic alkaloids and to develop resistance to synthetic chemicals used for its control. RNA interference (RNAi) is a natural mechanism that evolved as an immune response to double‐stranded RNA (dsRNA) viruses where dsRNA triggers silencing of target gene expression. RNAi is being developed as a method to control CPB. Here, we evaluated four CPB‐specific genes to identify targets for RNAi‐mediated control of this insect. Out of the four dsRNAs evaluated in CPB larvae and adults, dsIAP (dsRNA targeting inhibitor of apoptosis, iap gene) performed better than dsActin, dsHSP70, and dsDynamin in inducing larval mortality. However, in adults, the mortality induced by dsActin is significantly higher than the mortality induced by dsIAP, dsHSP70, and dsDynamin. Interestingly, a combination of dsIAP and dsActin performed better than either dsIAP or dsActin alone by inducing feeding inhibition in 24 hr and mortality in 48 hr in larvae. When the dsIAP and dsActin were expressed in the Escherichia coli HT115 strain and applied as a heat‐killed bacterial spray on potato plants, it protected the plants from CPB damage. These studies show that the combination of dsIAP and dsActin shows promise as an insecticide to control CPB.

Highly Variable Dietary RNAi Sensitivity Among Coleoptera

“…Notably, the authors observed over 60% mortality after 3 days of feeding on dsRNA targeting actin (see Supplementary Material in Xu et al, 2021). These studies with P. versicolora, together with that of Máximo et al (2020), who observed effective L. decemlineata mortality after 2 days, suggest that RNAi can work in a timely manner in some coleopterans, perhaps in particular chrysomelids of the subfamily Chrysomelinae. Furthermore, studies performed in chrysomelids collectively suggest high dietary RNAi efficacy via various sources of dsRNA consumption (e.g., RNAi cultivar., naked dsRNA, and bacterially expressed dsRNA).…”

First Sprayable Double-Stranded RNA-Based Biopesticide Product Targets Proteasome Subunit Beta Type-5 in Colorado Potato Beetle (Leptinotarsa decemlineata)

“…Colorado potato beetle has strong RNAi response to environmental RNA as demonstrated by dsRNA targeting different genes under different experimental conditions in the laboratory and field ( Máximo et al, 2020 ; Mehlhorn et al, 2020 ; Petek et al, 2020 ). In our studies, we show consumption of leaf material treated with Ledprona caused larval death over time ( Figure 6 ).…”

“…Previous studies using dsRNA molecules to target insect essential genes have proven the susceptibility of CPB to RNAi and demonstrated the potential of this technology to control this pest ( Zhu et al, 2011 ; San Miguel and Scott, 2016 ; Máximo et al, 2020 ; Mehlhorn et al, 2020 ; Petek et al, 2020 ; Doğan et al, 2021 ). However, one of the key known limitations of this approach was the capacity to scale dsRNA production at a low cost.…”

Lab-to-Field Transition of RNA Spray Applications – How Far Are We?

“…Host-induced gene silencing-mediated control of insect pests has been proven effective with an average of 50% conferred resistance (Koch and Wassenegger, 2021). Exogenous dsRNA and siRNA applications (e.g., feeding, injection, and oral delivery) to various insect pests and mites is routinely conducted to study gene function or identify RNAi targets (Lü et al, 2020;Mehlhorn et al, 2020Mehlhorn et al, , 2021Máximo et al, 2020). In line with the above discussion about RNAs that remain on sprayed surfaces and those that enter plant cells, insect pests and mites can ingest dsRNA and siRNAs by chewing-biting or piercing-sucking feeding behaviors.…”

“…For these purposes, encapsulation is pursued to guarantee and prolong the longevity of RNA sprays in the field. For example, E. coli is not only utilized for cost-effective dsRNA production but also represents a protective envelope for efficient dsRNA delivery (Lü et al, 2020;Máximo et al, 2020;Wang et al, 2021;Wu et al, 2021). Interestingly, encapsulation of dsRNA, if large enough, may prevent cellular uptake (plant intake) and thus shield dsRNA from plant DCL processing, as indicated by previous breakthroughs demonstrating that the expression of dsRNA in chloroplasts (DCL-free organelles) targeting the ßactin gene of L. decemlineata (Colorado potato beetle) caused larval lethality (Zhang et al, 2015).…”