Instar-dependent systemic RNA interference response in Leptinotarsa decemlineata larvae

Area of Science:

• Entomology
• Molecular Biology
• Pest Management

Background:

• RNA interference (RNAi) presents a viable strategy for managing Leptinotarsa decemlineata (Colorado potato beetle).
• The efficacy of RNAi is influenced by factors such as target gene, dsRNA concentration, and insect developmental stage.

Purpose of the Study:

• To evaluate RNAi efficiency targeting S-adenosyl-L-homocysteine hydrolase (LdSAHase) in different larval instars of L. decemlineata.
• To investigate the role of Dicer2 and Argonaute2 genes in RNAi efficiency and their response to dsRNA exposure.

Main Methods:

• Larvae were fed double-stranded RNA (dsRNA) targeting LdSAHase, and gene expression, survival, growth, and pupation were assessed.
• Expression levels of LdDcr2a, LdDcr2b, LdAgo2a, and LdAgo2b were analyzed following exposure to dsEGFP for varying durations.

Main Results:

• dsLdSAHase ingestion reduced LdSAHase expression, caused mortality, inhibited growth, and impaired pupation in an instar- and concentration-dependent manner.
• Expression of core RNAi genes (LdDcr2 and LdAgo2) was higher in younger larvae and initially upregulated by dsEGFP exposure, but downregulated with prolonged exposure.
• Previous dsEGFP exposure modulated the efficacy of dsLdSAHase, with short exposure enhancing and long exposure reducing target gene silencing and mortality.

Conclusions:

• RNAi efficiency in L. decemlineata is significantly influenced by larval instar and dsRNA concentration.
• The expression and activity of core RNAi machinery components (Dicer2, Argonaute2) play a crucial role in determining RNAi efficacy.
• Understanding these interactions is key to optimizing RNAi-based pest control strategies for L. decemlineata.