Sequence-Activity Relationships for the Snf7 Insecticidal dsRNA in Chrysomelidae

Area of Science:

• Agricultural Entomology
• Molecular Entomology
• RNA Interference (RNAi)

Background:

• Insecticidal double-stranded RNA (dsRNA) efficacy depends on length and sequence match.
• Western corn rootworm (WCR) requires ≥21 nt matches in DvSnf7 dsRNA for activity.
• Further data needed on <21 nt matches and the impact of multiple ≥21 nt matches.

Purpose of the Study:

• Characterize the sequence-activity relationship of insecticidal dsRNA.
• Determine the minimum effective sequence match length.
• Assess the impact of the number of 21 nt matches on dsRNA activity.

Main Methods:

• Compared activity of WCR dsRNA with 19, 20, and 21 nt contiguous matches.
• Evaluated orthologous Snf7 dsRNAs from Chrysomelid species against WCR and Colorado potato beetle (CPB).
• Quantified activity using LC50 values and correlated with the number of 21 nt matches.

Main Results:

• Neither 19 nor 20 nt sequence matches showed activity against WCR.
• A strong positive relationship observed between the number of 21 nt matches and WCR activity (lower LC50).
• Similar relationship found for CPB, with one exception possibly due to high polymorphism.

Conclusions:

• A ≥21 nt sequence match is essential for insecticidal dsRNA activity.
• Increased number of 21 nt matches generally enhances dsRNA efficacy.
• Findings can inform ecological risk assessments for dsRNA pesticides.