Knockdown of Helicoverpa armigera protease genes affects its growth and mortality via RNA interference

• Published in: Archives of insect biochemistry and physiology 2021-11, Vol.108 (3), p.e21840-n/a
• Main Authors: Vatanparast, Mohammad, Kazzazi, Majid, Sajjadian, Seyedeh Minoo, Park, Youngjin
• Format: Article
• Language: English
• Subjects: Bacteria; Bioassays; Biodegradation; Cathepsin L; Chymotrypsin; Cotton; Degradation; Double-stranded RNA; dsRNA; E coli; Enzymatic activity; Enzyme activity; Escherichia coli; Gene expression; Gene silencing; Genes; Helicoverpa armigera; Ingestion; Injection; Insect control; Insecticide resistance; Insecticides; Insects; Instars; Interference; Larvae; Midgut; Mortality; Oral administration; Pest control; Pesticides; Pests; Post-transcription; Protease; Proteinase; recombinant bacteria; Ribonuclease; Ribonucleic acid; RNA; RNA-mediated interference; RNAi; Trypsin
• ISSN: 0739-4462; 1520-6327
• DOI: 10.1002/arch.21840

Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), the cotton bollworm, is a destructive pest which is famous for its resistance to a variety of insecticides. RNA interference is a posttranscriptional gene silencing mechanism that has become a popular tool to control insect pests, triggered by double‐stranded RNAs (dsRNAs). The effect of ingestion and injection delivery methods of dsRNA related to some protease genes including Trypsin (Ha‐TRY39 and Ha‐TRY96), Chymotrypsin (Ha‐CHY), and Cathepsin L (Ha‐CAT) on growth and development of H. armigera was investigated in this study. All protease genes encoded full ORFs and were expressed in all H. armigera larvae stages and tissues. In both injection and feeding bioassays, Ha‐RNAi CHY's performance outperformed that of other protease genes. CHY enzyme activity in the midgut of larvae was significantly reduced after treatment with ds‐HaCHY. Oral administration of ds‐CHY also resulted in significant mortality of H. armigera larvae. However, because of the high RNase activity in the midgut lumen of lepidoptera, a large amount of dsRNA was needed to effectively kill instars of H. armigera. To reduce dsRNA degradation, bacterial expression and dsRNA formulation were used. After oral administration, it was toxic to H. armigera larvae. Before oral administration, bacterial cells were sonicated to increase dsRNA release. The RNA interference efficiency of sonicated bacteria was significantly increased, resulting in higher larval mortality when administered orally. All of these findings point to Ha‐CHY as a new candidate for developing an effective dsRNA‐based pesticide for H. armigera control. Oral administration of E. coli HT115‐expressing double‐stranded RNA specific to Ha‐CHY (dsHa‐CHY) after sonication has insecticidal effect in Helicoverpa armigera larvae. Highlights In this study, the effect of ingestion and injection delivery methods of double‐stranded RNA (dsRNA) associated to various proteases genes, such as trypsin, chymotrypsin, and cathepsin L, on Helicoverpa armigera growth and development was examined. The performance of Ha‐RNAi specific to chymotrypsin surpassed that of other protease genes. Bacterial expression and dsRNA formulation were carried out in HT115 Escherichia coli to reduce dsRNA degradation. After oral administration of sonicated bacteria, H. armigera larvae were toxic to dsRNA specific to chymotrypsin overexpressed in E. coli.