Ingestion of antagomir or agomir of microRNA results in physiological changes and high mortality in Frankliniella occidentalis

The leaf disc-mediated dsRNA delivery system is known to be effective for screening lethal genes via ingestion of RNA interference (RNAi) against Frankliniella occidentalis. We constructed small non-coding RNA libraries from F. occidentalis and identified a total of 301 microRNAs (miRNAs). To evaluate the lethality of miRNA candidate genes for ingestion of RNAi, antagomir and agomir of Foc-miR-71, which targets chitin biosynthesis, and Foc-miR-14 and FocmiR-1000, which target apoptosis, were synthesized and ingested by F. occidentalis via the leaf disc-mediated dsRNA delivery system. Ingestion of antagomir and agomir of Foc-miR-71 exhibited considerable mortalities in adults at 120 h post-ingestion and in larvae at 48 h post-ingestion. Ingestion of antagomirs of Foc-miR-14 and Foc-miR-1000 also resulted in substantial mortalities in adults at 120 h post-ingestion. Global transcription profiles were altered when larvae or females were ingested with Foc-miR-71 antagomir. The transcription levels of cuticular protein genes were reduced in the larvae and females, implying that chitin biosynthesis and degradation pathways were disturbed, resulting in increased mortality. These results demonstrate that miRNA-targeting ingestion RNAi could effectively control F. occidentalis and that trans -genic plants expressing miRNA genes may be further developped as a potential method to control insecticide-resistant thrips.