Genome-Wide Transcription and Functional Analyses Reveal Heterogeneous Molecular Mechanisms Driving Pyrethroids Resistance in the Major Malaria Vector Anopheles funestus Across Africa

Abstract

Pyrethroid resistance in malaria vector, An. funestus is increasingly reported across Africa, threatening the sustainability of pyrethroid-based control interventions, including long lasting insecticidal nets (LLINs). Managing this problem requires understanding of the molecular basis of the resistance from different regions of the continent, to establish whether it is being driven by a single or independent selective events. Here, using a genome-wide transcription profiling of pyrethroid resistant populations from southern (Malawi), East (Uganda), and West Africa (Benin), we investigated the molecular basis of resistance, revealing strong differences between the different African regions. The duplicated cytochrome P450 genes (CYP6P9a and CYP6P9b) which were highly overexpressed in southern Africa are not the most upregulated in other regions, where other genes are more overexpressed, including GSTe2 in West (Benin) and CYP9K1 in East (Uganda). The lack of directional selection on both CYP6P9a and CYP6P9b in Uganda in contrast to southern Africa further supports the limited role of these genes outside southern Africa. However, other genes such as the P450 CYP9J11 are commonly overexpressed in all countries across Africa. Here, CYP9J11 is functionally characterized and shown to confer resistance to pyrethroids and moderate cross-resistance to carbamates (bendiocarb). The consistent overexpression of GSTe2 in Benin is coupled with a role of allelic variation at this gene as GAL4-UAS transgenic expression in Drosophila flies showed that the resistant 119F allele is highly efficient in conferring both DDT and permethrin resistance than the L119. The heterogeneity in the molecular basis of resistance and cross-resistance to insecticides in An. funestus populations throughout sub-Saharan African should be taken into account in designing resistance management strategies.

Genome-wide gene expression profiling reveals that cuticle alterations and P450 detoxification are associated with pyrethroid resistance in Anopheles arabiensis populations from Ethiopia

“…Last, gstd3 was significantly overexpressed for each comparison of a resistant population against a susceptible strain (Figure 3, Table S3). Gstd3 overexpression has been reported for several pyrethroid and DDT resistant Anopheles populations 35, 68, 69 , but at present the role of delta class GSTs is thought to be minor compared to those of the epsilon class (e.g., GSTE2, see above) and functional validation of the interaction between GSTD3 and DDT/deltamethrin is needed to understand the contribution of this GST towards DDT/deltamethrin resistance. 68…”

“…34 Finally, glutathione-S-transferases (GSTs) are also important enzymes involved in toxicokinetic resistance mechanisms against pyrethroids. 35–38 For example, Riveron et al 2014, 2017, showed that allelic variation and higher transcription of GSTe2 confers resistance against permethrin in an An. gambiae population of Benin.…”

“…gambiae population of Benin. 35, 36 However, the role of such GST-based quantitative and qualitative changes has not yet been investigated in pyrethroid resistant An. arabiensis .…”

Genome‐wide gene expression profiling reveals that cuticle alterations and P450 detoxification are associated with deltamethrin and DDT resistance in Anopheles arabiensis populations from Ethiopia

“…Notably, in addition to epicuticular hydrocarbon enrichment, compositional changes of the cuticle have also been associated with insecticide resistance and several genes have been associated with the phenomenon . Finally, glutathione‐S‐transferases (GSTs) are also important enzymes involved in toxicokinetic resistance mechanisms against pyrethroids . For example, Riveron et al 2014, 2017, showed that allelic variation and higher transcription of GSTe2 confers resistance against permethrin in an An.…”

“…For example, Riveron et al 2014, 2017, showed that allelic variation and higher transcription of GSTe2 confers resistance against permethrin in an An. funestus population of Benin . However, the role of such GST‐based quantitative and qualitative changes has not yet been investigated in pyrethroid resistant An.…”