Topical dsRNA delivery induces gene silencing and mortality in the pea aphid

Abstract

BACKGROUND: With the growing number of available aphid genomes and transcriptomes, an efficient and easy-to-adapt tool for gene function study is urgently required. RNA interference (RNAi), as a post-transcriptional gene silencing mechanism, is important as a research tool for determining gene functions and has potential as a novel insect control strategy. However, these applications have been hampered by the lack of effective dsRNA delivery approaches in aphids. RESULTS:Here, we developed a convenient and efficient dsRNA delivery method, topical RNAi, in aphids. An investigation of its dose and time-dependent RNAi efficiencies revealed that with as little as 60 ng dsRNA per adult pea aphid (Acyrthosiphon pisum), the indicator gene, Aphunchback, could be significantly silenced within 2 h of exposure. The method was further validated by successfully silencing other different genes, and it was also efficient toward two other aphid species, Aphis citricidus and Myzus persicae. Furthermore, a noticeable mortality was also observed in pea aphids using topical RNAi-mediated gene silencing, within 4 days post-dsRNA application for four out of seven tested genes. CONCLUSION: Compared with the currently used dsRNA delivery methods in aphids, microinjection and ingestion, topical RNAi is time-and cost-effective, which could greatly influence RNAi-based gene functional studies and potential candidate gene selection for developing RNAi-based aphid control strategies in the future.

The Roles of DNA Methyltransferases 1 (DNMT1) in Regulating Sexual Dimorphism in the Cotton Mealybug, Phenacoccus solenopsis

“…Therefore, we tried two different RNAi methods to deliver siRNA into the cotton mealybugs. RNAi delivery methods have been documented in various insects, including hemipteran species [29,37,[49][50][51][52]. The microinjection method is the most common method for RNAi delivery in scientific research and is time-consuming and requires a high degree of technical skill.…”

“…In each treatment, 30 adult gravid females were pooled into a single biological replicate and injected with 0.5 µg siRNA each. Approximately 30 pupae in each biological replicate were treated using the topical RNAi-based siRNA delivery method in which a few drops were applied to the dorsal side of the pupa abdomen at a final concentration of~500 ng/µL following the methods described by [37]. The control groups underwent the same procedures under the same conditions, and all experiments were performed in triplicate.…”

Assessment of insecticidal effects and selectivity of CAPA‐PK peptide analogues against the peach‐potato aphid and four beneficial insects following topical exposure

“…Although, topical exposure of the pea aphid nymphs to biopesticides (i.e. target gene-specific dsRNA) was reported to be effective, 24 no previous study has reported topical exposure of aphids to peptide analogues. In this study, after treatment with CAPA-PK analogues, two effects were observed, namely a rapid effect (within 5 days) on survival was recorded for 17%-47% of the aphids while a long-lived effect on fecundity was observed in surviving aphids.…”

Expression Dynamics of Core RNAi Machinery Genes in Pea Aphids Upon Exposure to Artificially Synthesized dsRNA and miRNAs

“…RNAi (normally inferred to as the siRNA pathway) is a promising tool for aphid control [32][33][34] but RNAi use in effective pest control remains a challenge. This is due to gene silencing efficacies (both RNA and protein level), pest control efficacy (mortality), field delivery systems and potential resistance development [44].…”

“…However, these genes are rarely investigated using experimental approach. There is a need to study three pathways of RNAi activity as a possible aphid control strategy [32][33][34]. To explore the potential role of these expanded genes in three sub-pathways of RNAi, the expressions of 25 core RNAi genes were detected in different development stages, various tissues, dsRNA-treated samples, and miRNA-treated samples.…”