Phenotypic screen for RNAi effects in the codling moth Cydia pomonella

Area of Science:

• Entomology
• Molecular Biology
• Pest Management

Background:

• RNA interference (RNAi) offers a promising avenue for developing novel pest management strategies.
• Lepidopteran insects, such as the codling moth (Cydia pomonella), exhibit reduced susceptibility to RNAi-induced gene silencing compared to other insect taxa.
• Understanding RNAi induction in C. pomonella is crucial for its application in controlling this significant agricultural pest.

Purpose of the Study:

• To investigate the feasibility and efficacy of RNAi in the codling moth, Cydia pomonella.
• To identify specific genes and RNAi triggers (dsRNA and siRNA) that can induce a measurable effect in C. pomonella larvae.
• To assess the impact of RNAi targeting specific genes on larval growth and development.

Main Methods:

• Fluorescently labeled small interfering RNA (siRNA) and double-stranded RNA (dsRNA) targeting green fluorescent protein (GFP) were administered to neonate larvae on artificial diet to assess tissue distribution.
• A screen of dsRNAs targeting C. pomonella orthologs of Drosophila melanogaster genes (Cpcul1, Cpmle, Cpmsi, CpHbx, Cppum) was conducted.
• Larval growth, viability, and transcript levels (using qRT-PCR) were measured following dsRNA treatment. Effects of siRNA targeting Cpcul1 were also evaluated.

Main Results:

• Fluorescence from labeled RNA was primarily localized to the midgut of C. pomonella larvae.
• Double-stranded RNA targeting the cullin-1 gene (Cpcul1-dsRNA) significantly reduced larval growth, with treated larvae averaging 3mm compared to 4mm in controls.
• Cpcul1-dsRNA induced a dose-dependent reduction in Cpcul1 transcript levels, confirming RNAi efficacy. Cpcul1-siRNA produced a similar stunting effect.

Conclusions:

• RNAi can be induced in the codling moth, Cydia pomonella, with observable effects on larval development.
• Targeting the Cpcul1 gene with either dsRNA or siRNA effectively stunts larval growth, indicating its potential as a target for RNAi-based pest control.
• Despite growth inhibition, Cpcul1-dsRNA-treated larvae completed their life cycle, suggesting potential for resistance or the need for targeting essential developmental genes.