|Rodrigues, Thais - University Of Kentucky|
|Rieske, Lynne - University Of Kentucky|
|Palli, Subba - University Of Kentucky|
Submitted to: Scientific Reports
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/28/2017
Publication Date: 8/7/2017
Citation: Rodrigues, T.B., Rieske, L.K., Duan, J.J., Palli, S.R. 2017. Development of RNAi method for screening candidate genes to control emerald ash borer, Agrilus planipennis. Scientific Reports. 7: 7379.
Interpretive Summary: A new generation of insect control using RNA interference (RNAi) has emerged as a useful tool in insect pest management. The ingestion of double-strand RNA (dsRNA) can silence essential genes, causing delayed development or insect mortality. In this work, we developed a bioassay for oral delivery of dsRNA to an invasive forest and urban tree pest, the emerald ash borer (EAB - Agrilus planipennis). EAB feeds and develops beneath the bark, killing trees rapidly. This behavior, and the lack of an artificial diet for larvae and adults, makes their study very difficult. We found that dsRNA is transported and processed by EAB larvae three days after ingestion, and target genes in EAB neonates were silenced after five days feeding, with mortality after 10 days. This is the first study showing mortality and gene silencing in EAB larvae feeding on dsRNA. The results may be useful for studies to control other insect pests and for the future development of a non-toxic pesticide specific for EAB and/or a tree resistance.
Technical Abstract: Emerald ash borer (EAB), a serious invasive forest pest in the United States, has killed millions of North American ash trees and spread to 29 states since it was first detected in 2002 in southern Michigan. Development of a new control method that specifically targets the pest but has no adverse impacts on environment and other organisms is ideal for integration with biocontrol programs to effectively manage this invasive forest pest. In the laboratory, two double-stranded RNAs (dsIAP and dsCOP) were delivered to newly hatching EAB larvae via sucrose droplets and the mortality of exposed larvae was observed following the exposure treatments. Results from our study showed that dsRNA was transported and processed in siRNAs by EAB larvae 72h after feeding exposure. Also, dsIAP and dsCOP silenced their target genes in EAB neonates after 5 days feeding on dsRNA, and mortality was observed after 10 days. Mortality was increased by 1) increasing the dsRNA concentration; and 2) sequential exposure of the two different dsRNAs. This study will help to develop a non-toxic, RNAi-based pesticide specifically targeting EAB that can be integrated with the current EAB biocontrol program.