Systemic RNAi in the small hive beetle (Aethina tumida Murray, Coleoptera: Nitidulidae), a serious pest of the European honey bee (Apis mellifera)

Abstract

BACKGROUND: Aethina tumida is a serious pest of the European honey bee (Apis mellifera) in North America and Australia. Here we investigate whether Laccase 2, phenoloxidase gene essential for cuticle sclerotization and pigmentation in many insects, and vacuolar-ATPase V-type subunit A, vital for the generation of proton gradients used to drive a range of transport processes, could be potential targets for RNAi-mediated control of A. tumida. RESULTS: Injection of V-ATPase subunit A (5 ng) and Laccase 2 (12.5 ng) dsRNAs resulted in 100 % larval mortality, qPCR confirmed significant decreases and enhanced suppression of transcript levels over time. Oral delivery of V-ATPase subunit A dsRNA in solutions resulted in 50 % mortality, however gene suppression could not be verified. We suggest that the inconsistent RNAi effect was a consequence of dsRNA degradation within the gut due to the presence of extracellular nucleases. Target specificity was confirmed by a lack of effect on survival or gene expression in honey bees injected with A. tumida dsRNAs. CONCLUSIONS: This is the first study to show evidence for systemic RNAi in A. tumida in response to injected dsRNA but further research is required to develop methods to induce RNAi effects via ingestion.