The ci-miR-5 regulates the CiCYP18A1 to control moulting process of Chilo infuscatellus: Prospective target for pest...

The microRNAs (miRNAs) play an important role in the regulation of gene expression, influencing the outcome of many biological processes in insects. The introduction of miRNA into the insect body can lead to pest developmental abnormalities indicating that miRNAs are potential targets for pest control. In this study, we employed small RNA sequencing to characterise and analyse the expression of miRNAs in the sugarcane shoot borer Chilo infuscatellus (Snellen). By integrating previously published transcriptome sequencing data, we predicted and identified miRNAs and their target genes involved in the ecdysone metabolic pathway. We confirmed the target relationships between Ci-miR-4, Ci-miR-5 and CiCYP18A1 by RT-qPCR and dual-luciferase reporter assays in vivo and in vitro. Additionally, injection of miRNA mimics reduced the transcripts of CiCYP18A1 and led to abnormal moulting, which is similar to the defect phenotype of depletion of CiCYP18A1 by dsRNA. Furthermore, we also mixed the synthesised Ci-miR-5 mimic into artificial diets and found similar stunting results of the injection method. These results demonstrated that Ci-miR-5 could target CiCYP18A1 to regulate the moulting process and the successful use of an insect miRNA for gene silencing studies in this sugarcane pest. The method provided an effective novel approach for future RNAi-based pest control strategies.