Environmental RNAi pathways in the two-spotted spider mite

Area of Science:

• Molecular Biology
• Genetics
• Entomology

Background:

• RNA interference (RNAi) regulates gene expression via small RNA effectors.
• RNAi is a promising tool for arthropod pest control, with feeding being a convenient delivery method.
• The two-spotted spider mite (Tetranychus urticae) is a significant agricultural pest with high pesticide resistance, making it a target for RNAi.

Purpose of the Study:

• To investigate the fate of ingested RNAs in Tetranychus urticae.
• To identify features and conditions affecting small RNA biogenesis from external RNA sources.
• To inform the rational design of RNAi triggers for spider mite control.

Main Methods:

• Biochemical and sequencing approaches were employed.
• Extensive computational assessment was used to analyze RNA metabolism.
• Processing of synthetic and plant-derived RNAs ingested by mites was evaluated.

Main Results:

• Tetranychus urticae exhibits a modest response to oral RNAi, with distinct biogenesis pathways compared to model organisms.
• Trans-acting small RNAs derived from ingested RNAs were found to be unstable and rare.
• Degradation fragments were distinguished from active RNAi pathway substrates.

Conclusions:

• Most ingested RNA transcripts are degraded in spider mites, with limited conversion into gene-regulating molecules.
• The rarity of stable, trans-acting small RNAs from dietary sources suggests an adaptive trait to avoid generating diverse gene regulators from food.
• This research offers a framework for evaluating RNAi technology in organisms lacking extensive genetic and biochemical tools, aiding in the design of effective RNAi strategies for T. urticae.