Mechanisms of Cell Entry by dsRNA Viruses: Insights for Efficient Delivery of dsRNA and Tools for Improved RNAi-Based Pest Control

Abstract

While RNAi is often heralded as a promising new strategy for insect pest control, a major obstacle that still remains is the efficient delivery of dsRNA molecules within the cells of the targeted insects. However, it seems overlooked that dsRNA viruses already have developed efficient strategies for transport of dsRNA molecules across tissue barriers and cellular membranes. Besides protecting their dsRNA genomes in a protective shell, dsRNA viruses also display outer capsid layers that incorporate sophisticated mechanisms to disrupt the plasma membrane layer and to translocate core particles (with linear dsRNA genome fragments) within the cytoplasm. Because of the perceived efficiency of the translocation mechanism, it is well worth analyzing in detail the molecular processes that are used to achieve this feat. In this review, the mechanism of cell entry by dsRNA viruses belonging to the Reoviridae family is discussed in detail. Because of the large amount of progress in mammalian versus insect models, the mechanism of infections of reoviruses in mammals (orthoreoviruses, rotaviruses, orbiviruses) will be treated as a point of reference against which infections of reoviruses in insects (orbiviruses in midges, plant viruses in hemipterans, insect-specific cypoviruses in lepidopterans) will be compared. The goal of this discussion is to uncover the basic principles by which dsRNA viruses cross tissue barriers and translocate their cargo to the cellular cytoplasm; such knowledge subsequently can be incorporated into the design of dsRNA virus-based viral-like particles for optimal delivery of RNAi triggers in targeted insect pests.

Assessment of Sesamia nonagrioides (Lepidoptera: Noctuidae) EcR and USP Genes as Targets for Exogenous Non-Persistent RNAi

“…The research presented here provides useful information: that targeting S. nonagrioides EcR and USP genes by RNAi did not result in important developmental defects and mortalities that could be assessed positively in designing of an RNAi-based pesticide to combat this important pest of corn. RNAi technology is one of the most recent trends in the field of crop protection and conceptually approaches the "ideal" of the perfect pesticide: it targets only the intended pest and is predicted to have minimal impact on the non-target organisms (pollinators, parasitoids, predators, and vertebrates) [15,[53][54][55]. Furthermore, it is biodegradable and therefore with minimal risk for human health and the environment [15,[53][54][55].…”

“…RNAi technology is one of the most recent trends in the field of crop protection and conceptually approaches the "ideal" of the perfect pesticide: it targets only the intended pest and is predicted to have minimal impact on the non-target organisms (pollinators, parasitoids, predators, and vertebrates) [15,[53][54][55]. Furthermore, it is biodegradable and therefore with minimal risk for human health and the environment [15,[53][54][55]. The use of this technology to control Lepidopteran pests and more specifically S. nonagrioides needs a considerable improvement for the reasons mentioned previously.…”

“…Technologies that were proved to be efficient in modern medicine that involve RNAi, e.g., Virus Like Particles, Ribonucleoproteins, etc., must be investigated in RNAi-mediated pest control. These technologies are estimated to be able to overcome all obstacles that insect cells pose to RNAi and the future for the mass production of RNAi pesticides lies ahead [15,[53][54][55].…”

Engineering strategies for insect viruses and microbes for dsRNA production and delivery to insects for targeted gene silencing

“…To develop VLPs for dsRNA delivery to insect pest, dsRNA viruses would probably be the best candidates because they can naturally encapsulate long dsRNA genomes in their virus capsid (Swevers et al 2021), whereas how big and how much of the dsRNA molecules can be assembled inside the VLP are interesting questions. Besides, how to assemble dsRNA molecules inside the VLPs is a big challenge.…”

“…There is an accumulating but limited body of research and review articles on insect viruses and microbes as biotechnological resources for application against insect pests (Kolliopoulou et al 2017;Swevers et al 2021). Viruses have several attractive properties such as efficiency and specificity of infection that make them excellent dsRNA delivery vehicles.…”