Global, asynchronous partial sweeps at multiple insecticide resistance genes in Aedes mosquitoes

Area of Science:

• Genomics and Evolutionary Biology
• Medical Entomology
• Vector-Borne Disease Control

Background:

• Aedes aegypti and Aedes albopictus mosquitoes are primary vectors of dengue, a significant global health concern.
• Widespread insecticide use has driven the evolution of resistance in these mosquito populations, complicating disease control efforts.
• The genetic basis and geographic dissemination of insecticide resistance in these vectors are not fully understood.

Purpose of the Study:

• To investigate partial selective sweeps at insecticide resistance genes on two chromosomes in Aedes mosquitoes.
• To characterize the geographical spread of these resistance-associated genetic changes.
• To understand the genetic architecture and evolutionary dynamics of insecticide resistance in globally invasive mosquito species.

Main Methods:

• Analysis of partial selective sweeps at resistance genes, specifically the voltage-sensitive sodium channel (VSSC) gene on chromosome 3 and a locus on chromosome 2.
• Identification of nucleotide substitutions associated with resistance in Aedes aegypti and Aedes albopictus.
• Characterization of copy number variation and genetic backgrounds within glutathione S-transferase (GST) epsilon class genes.

Main Results:

• Partial selective sweeps were identified at the VSSC gene on chromosome 3, with distinct resistance-associated substitutions in Ae. albopictus and Ae. aegypti.
• In Ae. aegypti, sweeps were also found at a chromosome 2 locus containing 15 GST epsilon class genes, exhibiting significant copy number variation.
• Three distinct GST genetic backgrounds have spread across major geographical regions, suggesting independent evolutionary trajectories and spread patterns for VSSC and GST loci.

Conclusions:

• Insecticide resistance genes, including VSSC and GSTs, are undergoing rapid global spread in invasive Aedes mosquito populations.
• The independent evolution and spread of resistance mechanisms, particularly at the F1534C substitution in VSSC, underscore the adaptability of these vectors.
• Glutathione S-transferase (GST) genes play a critical role in insecticide resistance evolution and exhibit complex geographical distribution patterns.