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1. The Interplay Between Viruses and RNAi Pathways in Insects

   https://doi.org/10.1146/annurev-ento-033020-090410  

   Bonning, Bryony C.; Saleh, Maria-Carla (January 2021, Annual Review of Entomology)

   null (Ed.)

   As an overarching immune mechanism, RNA interference (RNAi) displays pathogen specificity and memory via different pathways. The small interfering RNA (siRNA) pathway is the primary antiviral defense mechanism against RNA viruses of insects and plays a lesser role in defense against DNA viruses. Reflecting the pivotal role of the siRNA pathway in virus selection, different virus families have independently evolved unique strategies to counter this host response, including protein-mediated, decoy RNA–based, and microRNA-based strategies. In this review, we outline the interplay between insect viruses and the different pathways of the RNAi antiviral response; describe practical application of these interactions for improved expression systems and for pest and disease management; and highlight research avenues for advancement of the field. 

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2. Insecticidal RNA interference, thinking beyond long dsRNA

   https://doi.org/10.1002/ps.6147  

   Flynt, A (October 2020, Pest management science)

   null (Ed.)

   Over 20 years ago double-stranded RNA (dsRNA) was described as the trigger of RNAi interference (RNAi)-based gene silencing. This paradigm has held since, especially for insect biopesticide technologies where dsRNAs, similar to those described in 1998, are used to inhibit gene expression. In the intervening years, investigation of RNAi pathways has revealed the small RNA effectors of RNAi are diverse and rapidly evolving. The rich biology of insect small RNAs suggests potential to use multiple RNAi modes for manipulating gene expression. By exploiting different RNAi pathways, the menu of options for pest control can be expanded and could lead to better tailored solutions. Fortunately, basic delivery strategies used for dsRNA such as direct application or transgenic expression will translate well between RNAs transiting different RNAi pathways. Importantly, further engineering of RNAi-based biopesticides may provide an opportunity to address dsRNA insensitivity seen in some pests. Characterization of RNAi pathways unique to target species will be indispensable to this end and may require thinking beyond long dsRNA. 

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3. Exploiting somatic piRNAs in Bemisia tabac i enables novel gene silencing through RNA feeding

   https://doi.org/10.26508/lsa.202000731  

   Mondal, Mosharrof; Brown, Judith K; Flynt, Alex (August 2020, Life Science Alliance)

   null (Ed.)

   RNAi promises to reshape pest control by being nontoxic, biodegradable, and species specific. However, due to the plastic nature of RNAi, there is a significant variability in responses. In this study, we investigate small RNA pathways and processing of ingested RNAi trigger molecules in a hemipteran plant pest, the whitefly Bemisia tabaci . Unlike Drosophila , where the paradigm for insect RNAi technology was established, whitefly has abundant somatic piwi-associated RNAs (piRNAs). Long regarded as germline restricted, piRNAs are common in the soma of many invertebrates. We sought to exploit this for a novel gene silencing approach. The main principle of piRNA biogenesis is the recruitment of target RNA fragments into the pathway. As such, we designed synthetic RNAs to possess complementarity to the loci we annotated. Following feeding of these exogenous piRNA triggers knockdown as effective as conventional siRNA-only approaches was observed. These results demonstrate a new approach for RNAi technology that could be applicable to dsRNA-recalcitrant pest species and could be fundamental to realizing insecticidal RNAi against pests. 

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4. Double-stranded RNA binding protein, Staufen, is required for the initiation of RNAi in coleopteran insects

   https://doi.org/10.1073/pnas.1809381115  

   Yoon, June-Sun; Mogilicherla, Kanakachari; Gurusamy, Dhandapani; Chen, Xien; Chereddy, Shankar C.; Palli, Subba Reddy (August 2018, Proceedings of the National Academy of Sciences)

   RNA interference (RNAi) is being used to develop methods to control pests and disease vectors. RNAi is robust and systemic in coleopteran insects but is quite variable in other insects. The determinants of efficient RNAi in coleopterans, as well as its potential mechanisms of resistance, are not known. RNAi screen identified a double-stranded RNA binding protein (StaufenC) as a major player in RNAi. StaufenC homologs have been identified in only coleopteran insects. Experiments in two coleopteran insects, Leptinotarsa decemlineata and Tribolium castaneum , showed the requirement of StaufenC for RNAi, especially for processing of double-stranded RNA (dsRNA) to small interfering RNA. RNAi-resistant cells were selected by exposing L. decemlineata , Lepd-SL1 cells to the inhibitor of apoptosis 1 dsRNA for multiple generations. The resistant cells showed lower levels of StaufenC expression compared with its expression in susceptible cells. These studies showed that coleopteran-specific StaufenC is required for RNAi and is a potential target for RNAi resistance. The data included in this article will help improve RNAi in noncoleopteran insects and manage RNAi resistance in coleopteran insects. 

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5. Chloroplast Genome Engineering: A Plausible Approach to Combat Chili Thrips and Other Agronomic Insect Pests of Crops

   https://doi.org/10.3390/plants12193448  

   Bulle, Mallesham; Sheri, Vijay; Aileni, Mahender; Zhang, Baohong (October 2023, Plants)

   The world population’s growing demand for food is expected to increase dramatically by 2050. The agronomic productivity for food is severely affected due to biotic and abiotic constraints. At a global level, insect pests alone account for ~20% loss in crop yield every year. Deployment of noxious chemical pesticides to control insect pests always has a threatening effect on human health and environmental sustainability. Consequently, this necessitates for the establishment of innovative, environmentally friendly, cost-effective, and alternative means to mitigate insect pest management strategies. According to a recent study, using chloroplasts engineered with double-strand RNA (dsRNA) is novel successful combinatorial strategy deployed to effectively control the most vexing pest, the western flower thrips (WFT: Frankliniella occidentalis). Such biotechnological avenues allowed us to recapitulate the recent progress of research methods, such as RNAi, CRISPR/Cas, mini chromosomes, and RNA-binding proteins with plastid engineering for a plausible approach to effectively mitigate agronomic insect pests. We further discussed the significance of the maternal inheritance of the chloroplast, which is the major advantage of chloroplast genome engineering. 

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