RNAi of Ago1 and Ago2 Disrupts Molting in the White-Backed Planthopper (Sogatella furcifera)

Abstract

Argonaute (Ago) proteins are integral components of the RNA-induced silencing complex (RISC), regulate gene expression through RNAi, and are essential for embryogenesis and cellular morphogenesis in insects. However, today, little is known about their role in the molting development of insects. In this study, we have used the white-backed planthopper (Sogatella furcifera) as an important model and pest in agriculture, and we characterized and investigated the role of Ago-1 and Ago-2. In essence, the respective cDNA sequences of SfAgo1 and SfAgo2 contained 2823 and 3446 bp, and the respective encoded amino acids were 940 and 829. RT-qPCR revealed that Ago1 and Ago2 were expressed in all life stages as the nymphs that undergo molting, also in all tissues as the integument that is involved in new cuticle synthesis and chitin metabolism. Following RNAi, the lethal phenotypes showed molting failure, and typically, the expression levels of the chitin metabolic pathway genes and Dicer were significantly reduced. Similarly, transcriptome analysis revealed considerable enrichment of the GO terms structural constituent of cuticle, chitin catabolic progress, chitin binding, amino sugar and nucleotide sugar metabolism, and aminoglycan catabolic process upon RNAi of Ago1 and Ago2. Altogether, our findings indicate that Ago-1 and Ago-2 play a pivotal role in molting and new cuticle formation of insects. The data are discussed in relation to potential mechanisms and the use of RNAi in pest insect control.