Oral ingestion of heat shock protein 70 dsRNA is lethal under normal and thermal stress conditions in the sweetpotato whitefly, Bemisia tabaci

The sweetpotato whitefly, Bemisia tabaci, is a serious pest of various horticultural crops worldwide. Since 1990s, B. tabaci has been invaded into many countries due to climate change and global trades of agricultural products. Due to the rapid development of pesticide resistance, alternative techniques have been required for the control of B. tabaci. Here, we investigated whether oral ingestion of dsRNA induced knockdown in whiteflies. Double-stranded RNA (dsRNA) targeting heat shock protein 70 (hsp70) mRNA was produced from cDNA using specific primers. Adult whiteflies (less than 12 h post-eclosion) were allowed to ingest 20% (w/v) sucrose solution containing hsp70 dsRNA in a 2-layered membrane feeding tube. Individual whiteflies ingested 16.9 ng dsRNA on an average in 24 h Quantitative real-time PCR analysis showed that dsRNA ingestion decreased the mRNA level of hsp70 in a dose-dependent manner, and the hsp70 knockdown was sustained for at least 3 days. Furthermore, dsRNA-treated whiteflies showed increased mortality after 3 days of incubation at 25 °C. Mortality was prompted by heat shock but not by cold shock treatments. Our data suggest that the oral delivery of dsRNA had excellent efficacy for the RNAi treatment of whiteflies and that the expression of hsp70 was critical for the survival of B. tabaci, regardless of the temperature conditions.