Journal Article

Allelic variation in a cluster of epsilon glutathione S-transferase genes contributes to DDT and pyrethroid resistance in the major African malaria vector Anopheles funestus

Kouamo, Mersimine F. M., Gadji, Mahamat, Muhammad, Abdullahi, Hearn, Jack, Wondji, Charles S., Ibrahim, Sulaiman S.

2025

Overview

Background Insecticide resistance in malaria vectors is a serious challenge to malaria control and elimination. Elucidation of the role of detoxification genes in resistance is necessary to develop targeted strategies to reduce malaria burden. Glutathione S-transferase epsilon clusters ( GSTe genes) are upregulated in DDT- and pyrethroid-resistant Anopheles funestus mosquitoes across Africa. However, except for GSTe2 , the molecular mechanisms behind this upregulation remain unclear. Here, we established that overexpression and allelic variation of GSTe genes contribute to insecticide resistance in African malaria vector An. funestus s.s. Methods Transcriptomic and genomic analyses of GST e genes were conducted, followed by in silico structural analysis, and functional characterization of GSTe3 , GSTe4 and GSTe6 using metabolic assay and transgenic expression in Drosophila flies. Results Transcriptomic and genomic analyses reveal changes in gene expression and genetic diversity of GSTes cluster in An. funestus across Africa. Cloning of cDNAs of GST es from different regions of Africa detected allelic variants under selection, including A 17 D 26 T 158 -GSTe3, L 135 H 191 A 189 -GSTe4 in West/Central Africa, and T 169 S 201 E 210 - GST e6 present only in West/Southern Africa. Furthermore, in silico analysis of BN-GSTe3, MWI-GSTe3, BN-GSTe4, MWI-GSTe4, CMR-GSTe6 and, BN-GSTe6 alleles revealed that allelic variations increase the binding cavity in the active site of these GST es with stronger affinities observed towards DDT and permethrin. All recombinant GST es significantly metabolize DDT (41–63%) and permethrin (13–25%). Additionally, BN-GSTe4 (L 135 H 191 A 189 -GSTe4) variant significantly metabolizes deltamethrin (28.75%), compared to the wild-type allele (15.99%; p  < 0.05). Transgenic expression of the GST es in Drosophila melanogaster flies revealed reduced DDT mortalities in flies expressing the selected alleles (39–55%; p˂0.001), compared to control group (98%). Similar resistance patterns were observed toward permethrin and deltamethrin. Conclusion These findings established the role of GST es in conferring cross-resistance to pyrethroids and DDT, highlighting the role of these genes in metabolic resistance in An. funestus , which complicates malaria control using the above key insecticides.

• Publisher: BioMed Central,BioMed Central Ltd,Springer Nature B.V,BMC
• Subject: Africa / Alleles / Amino acids / Analysis / Animal Genetics and Genomics / Animals / Anopheles - drug effects / Anopheles - enzymology / Anopheles - genetics / Anopheles funestus / Biomedical and Life Sciences / Cloning / Clusters / Cross-resistance / Cytochrome / DDT / DDT - pharmacology / Deltamethrin / Detoxification / Dosage and administration / Fruit flies / Gene expression / Genes / Genetic diversity / Genetic Variation / Genomes / Genomic analysis / Glutathione / Glutathione S-transferase / Glutathione transferase / Glutathione Transferase - chemistry / Glutathione Transferase - genetics / Glutathione Transferase - metabolism / Haplotypes / Insect Proteins - chemistry / Insect Proteins - genetics / Insect Proteins - metabolism / Insecticide resistance / Insecticide Resistance - genetics / Insecticides / Insecticides - pharmacology / Life Sciences / Ligands / Malaria / Malaria - transmission / Metabolic resistance / Metabolism / Microarrays / Microbial Genetics and Genomics / Molecular modelling / Mosquito Vectors - drug effects / Mosquito Vectors - genetics / Mosquitoes / Multigene Family / Mutation / Permethrin / Pesticide resistance / Plant Genetics and Genomics / Prevention / Proteomics / Pyrethrins - pharmacology / Pyrethroids / pyrethroids/DDT / Risk factors / Structural analysis / Structure-function relationships / Transcriptomics / Transgenic expression, metabolic assay / Vector-borne diseases / Vectors / Vectors (Biology)