# Cyantraniliprole and Thiamethoxam Exposure Changes Expression of Transcripts Associated with Small Non-Coding RNA Processing in the Colorado Potato Beetle

## TL;DR

This study explores how insecticides affect gene expression in Colorado potato beetles, revealing key genes involved in insecticide resistance.

## Contribution

The study identifies specific transcripts linked to small non-coding RNA processing that are modulated by insecticide exposure in Colorado potato beetles.

## Key findings

- Cyantraniliprole exposure alters Ago1 and Dcr2b transcript levels in beetles.
- Thiamethoxam exposure affects Dcr2a and Siwi-1 transcript levels.
- Reducing Ago1 expression increases beetle susceptibility to cyantraniliprole.

## Abstract

The Colorado potato beetle is known for its ability to cause significant damage to potato crops worldwide. Unfortunately, this insect is also capable of developing substantial resistance against different compounds deployed to regulate its spread. A better understanding of the molecular basis underlying this resistance is key in order to develop novel strategies aimed at this potato pest. The goal of the current study was, thus, to characterize the expression of transcripts with likely relevance for insecticide resistance in Colorado potato beetles treated with two compounds of interest. Changes were observed for several transcripts in response to either low- or high-dose exposure, as well as for different time durations. The modulation of one transcript using RNAi was also associated with the increased susceptibility of insects treated with the insecticide cyantraniliprole. Overall, this information highlights potentially relevant targets for insecticide resistance in the Colorado potato beetle and reveals a transcript of interest for investigating further within the context of cyantraniliprole response in this pest.

The Colorado potato beetle (Leptinotarsa decemlineata (Say)) can cause extensive damage to agricultural crops worldwide and is a significant insect pest. This insect is notorious for its ability to evade various strategies deployed to control its spread and is known for its relative ease in developing resistance against different insecticides. Various molecular levers are leveraged by L. decemlineata for this resistance to occur, and a complete picture of the genes involved in this process is lacking. While small non-coding RNAs, including miRNAs, are differentially expressed in insects exposed to insecticides, levels of transcript coding for proteins underlying their synthesis remain to be characterized fully. The overarching objective of this work aims to fill that gap by assessing the expression of such targets in L. decemlineata exposed to cyantraniliprole and thiamethoxam. The expression status of Ago1, Ago2, Ago3, Dcr2a, Dcr2b, Expo-5, Siwi-1 and Siwi-2 transcripts were quantified via qRT-PCR in adult L. decemlineata treated with low and high doses of these compounds for different lengths of time. Variation in Ago1 and Dcr2b expression was notably observed in L. decemlineata exposed to cyantraniliprole, while thiamethoxam exposure was associated with the modulation of Dcr2a and Siwi-1 transcript levels. The down-regulation of Ago1 expression in L. decemlineata using dsRNA, followed by cyantraniliprole treatment, was associated with a reduction in the survival of insects with reduced Ago1 transcript expression. Overall, this work presents the insecticide-mediated modulation of transcripts associated with small non-coding RNA processing and showcases Ago1 as a target to further investigate its relevance in cyantraniliprole response.