RNAi-Mediated Silencing of the Chitinase 5 Gene for Fall Webworm (Hyphantria cunea) Can Inhibit Larval Molting Depending on the Timing of dsRNA Injection.

Abstract

Simple SummaryThe fall webworm, Hyphantria cunea, is a worldwide invasive pest causing serious ecological and economic damage. The use of RNAi is a feasible strategy for controlling this pest. In this study, we evaluated the importance of the chitinase 5 gene (HcCht5) in the development of H. cunea larvae. We found that the RNAi-mediated silencing of HcCht5 arrested molting and caused larval mortality depending on the dsRNA injection time. The silencing of HcCht5 down-regulated genes that were related to chitin metabolism, molting hormone signaling, and detoxification metabolism. Our findings indicate that HcCht5 is an important gene in regulating larval development and a promising target for RNAi-mediated pest management of the pest H. cunea.Chitinases, which are crucial enzymes required for chitin degradation and reconstruction, are often selectively considered to be effective molecular targets for pest control due to their critical roles in insect development. Although the Hyphantria cunea chitinase gene has been reported previously, its sequence characteristics, gene function, and feasibility as a potential target for pest management were absent. In the present study, we characterized the H. cunea chitinase gene and designated it HcCht5. Phylogenic and domain structure analysis suggested that HcCht5 contained the typical chitinase features and was clustered into chitinase group I. Tissue-specific and developmental expression pattern analysis with Real-Time Quantitative PCR (RT-qPCR) showed that HcCht5 was mainly expressed in the integument tissues and that the transcript levels peaked during molting. RNA interference (RNAi)-mediated silencing of HcCht5 caused 33.3% (2 ug) and 66.7% (4 ug) mortality rates after double-stranded RNA (dsRNA) injection. Importantly, the interference efficiency of HcCht5 depended on the injection time of double-stranded RNA (dsRNA), as the pre-molting treatment achieved molt arrest more effectively. In addition, transcriptome sequencing (RNA-seq) analysis of RNAi samples demonstrated silencing of the down-regulated HcCht5 genes related to chitin metabolism and molting hormone signaling, as well as genes related to detoxification metabolism. Our results indicate the essential role of HcCht5 in H. cunea development and detail the involvement of its gene function in the larval molting process.