# First Insights into the Comparative Transcriptomic Response of Field and Laboratory Aedes aegypti Strains to Partial-Mortality Concentration (<50%) Imidacloprid and Broflanilide Exposure

## TL;DR

This study compares how wild and lab mosquitoes respond to two insecticides at the gene level, revealing differences in their molecular reactions that could help improve insecticide strategies.

## Contribution

The study provides new insights into the transcriptomic responses of field and lab Aedes aegypti strains to sublethal insecticide exposure.

## Key findings

- Both insecticides activated genes related to protein degradation, detoxification, and structural changes in mosquitoes.
- The field strain showed more flexible gene responses, especially to imidacloprid, compared to the lab strain.
- Broflanilide triggered similar early responses in both strains, while imidacloprid amplified existing differences.

## Abstract

Aedes aegypti mosquitoes transmit viruses such as dengue, Zika and chikungunya and are mainly controlled with insecticides. However, many mosquito populations are becoming resistant, which reduces the effectiveness of these tools. In this study, we compared how two different populations of Aedes aegypti change their gene activity after being exposed to two insecticides: imidacloprid, a neonicotinoid, and broflanilide, a newer meta-diamide compound. One population was a field-derived strain from San Nicolás with a history of insecticide exposure, and the other was a fully susceptible laboratory strain called New Orleans. Using RNA sequencing, we measured which genes were turned on or off after a short, sublethal exposure to each insecticide. Both compounds caused strong changes in gene expression, mainly activating genes involved in protein degradation, membrane transport, detoxification and changes in the cuticle and cytoskeleton. We also found that the field population showed more flexible (plastic) gene responses than the laboratory strain, especially after exposure to imidacloprid. In contrast, early responses to broflanilide were more similar between populations. These results help us understand how different mosquito populations respond at the molecular level to new and repurposed insecticides and may support the design of better insecticide rotation strategies to delay resistance.

Insecticide resistance in Aedes aegypti (Linnaeus, 1762), the primary vector of several arboviruses, threatens vector control efficacy and motivates evaluation of current and candidate public health insecticides, such as imidacloprid and broflanilide, and their molecular impacts. Here, we used RNA sequencing (RNA-seq) to characterize the transcriptomic response to one-hour acute exposure to an operational partial-mortality concentration (<50%) of imidacloprid and broflanilide in two Ae. aegypti strains: a field-derived, pyrethroid-resistant population from San Nicolás and a susceptible laboratory strain (New Orleans). Adults were exposed for 1 h to partial-mortality concentration (<50%) doses of each insecticide or acetone control, and differential gene expression and Gene Ontology (GO) enrichment were assessed with DESeq2-based workflows. We detected pronounced baseline transcriptomic differences between strains and extensive activation of gene expression after insecticide exposure, with a strong bias toward up-regulation. A shared transcriptional core involving proteolysis, transmembrane transport, detoxification pathways, and structural remodeling of the cuticle and cytoskeleton was identified across contrasts. Despite these common elements, broflanilide elicited largely conserved early responses between strains, whereas imidacloprid amplified pre-existing divergence and produced marked population-specific transcriptional signatures. These findings suggest greater transcriptional changes in the field-derived strain, particularly in response to imidacloprid, and highlight the importance of integrating population-specific molecular information when designing insecticide rotation schemes and resistance management strategies targeting Ae. aegypti.