A Targeted RNAi-of-RNAi Strategy to Overcome Nuclease-Mediated RNAi Suppression and Enhance RNAi Efficacy in Lepidoptera Pest, Cydia Pomonella

The
codling moth has developed resistance to chemical
insecticides
and biological agents, necessitating alternative control strategies.
RNA interference (RNAi) offers considerable potential. However, variable
efficacy across target genes remains a major barrier in lepidopterans.
In this study, we identified three REase genes in the codling moth,
each containing a conserved PIN domain. CmREase1 and CmREase2 were strongly induced by exogenous dsRNA and showed
high expression in midgut and hemolymph. RNAi-mediated silencing of
these genes reduced dsRNA degradation in hemolymph and significantly
enhanced RNAi efficiency, confirming their key roles in dsRNA degradation
and suppression of RNAi. In contrast, CmREase4 was
dsRNA-responsive but had no detectable effect on RNAi efficiency.
Moreover, transcriptional profiling of Dcr-2 and AGO2 revealed that pretreatment with nonspecific dsEGFP followed by target-specific dsRNA markedly improved
RNAi efficacy, comparable to REase knockdown. Collectively, these
results demonstrate that REases are critical modulators of RNAi efficiency
in codling moth and provide a framework for RNAi-based biopesticide
development, offering new strategies to overcome variability in RNAi
responsiveness among lepidopteran pests.