Silencing of dre4 Contributes to Mortality of Phyllotreta striolata

SIMPLE SUMMARY: Biopesticides developed based on RNA interference (RNAi) are specific, efficient and environmentally friendly pesticides for the biological control of pests. Phyllotreta striolata is one of the most destructive pests of Cruciferae crops. RNAi is a promising alternative strategy for Phyllotreta striolata control, since the larvae of P. striolata feed on roots and the adults feed on leaves. However, little information on the lethal effects of RNAi is available for P. striolata. In this study, we identified that the dre4 gene, which plays a significant role in the process of gene transcription, DNA repair and DNA replication, is critical for P. striolata’s survival. We found that the silencing of dre4 contributed to the high mortality of P. striolata through microinjection and oral delivery. Moreover, we identified that transcripts of multiple gene-related signaling pathways were varied by the silencing of dre4, which might have caused the lethality of the P. striolata. Overall, our findings indicate that dre4 could be a fatal RNAi target to develop biopesticides for P. striolata management. ABSTRACT: The striped flea beetle, Phyllotreta striolata, is one of the most destructive pests of Cruciferae crops worldwide. RNA interference (RNAi) is a promising alternative strategy for pest biological control, which overcomes the weakness of synthetic insecticides, such as pest resistance, food safety problems and toxicity to non-target insects. The homolog of Spt16/FACT, dre4 plays a critical role in the process of gene transcription, DNA repair, and DNA replication; however, the effects of dre4 silencing in P. striolata remain elusive. In this study, we cloned and characterized the full-length dre4 from P. striolata and silenced Psdre4 through microinjection and oral delivery; it was found that the silencing of dre4 contributed to the high mortality of P. striolata in both bioassays. Moreover, 1166 differentially regulated genes were identified after Psdre4 interference by RNA-seq analysis, which might have been responsible for the lethality. The GO analysis indicated that the differentially regulated genes were classified into three GO functional categories, including biological process, cellular component, and molecular function. The KEGG analysis revealed that these differentially regulated genes are related to apoptosis, autophagy, steroid hormone biosynthesis, cytochrome P450 and other signaling pathways. Our results suggest that Psdre4 is a fatal RNAi target and has significant potential for the development of RNA pesticides for P. striolata management.