Transcriptome Sequencing and Analysis of Changes Associated with Insecticide Resistance in the Dengue Mosquito (Aedes aegypti) in Vietnam

Abstract

The mosquito Aedes aegypti is a transmission vector for dangerous epidemic diseases in humans. Insecticides have been used as the most general vector control method in the world. However, Ae. aegypti have developed many resistant mechanisms such as reduced neuronal sensitivity to insecticides (target-site resistance), enhanced insecticide metabolism (metabolic resistance), altered transport, sequestration, and other mechanisms. It has become a major problem for vector control programs. Transcriptome sequencing and bioinformatic analysis were used to compare transcription levels between a susceptible strain (Bora7) and a resistant strain (KhanhHoa7) collected from the field. A total of 161 million Illumina reads, including 66,076,678 reads from the Bora7 strain and 69,606,654 reads from the KhanhHoa7 strain, were generated and assembled into 11,174 genes. A comparison of the KhanhHoa7 transcriptome to that of Bora7 showed 672 upregulated genes and 488 downregulated genes. We identified the highly upregulated genes: cytochrome P450 4C1, 4C3, 4C21, 4D1, 4D1 isoform X2, 4D2, 4D2 isoform X2, 4G15, 6A2, 6A8, 6D3, and 9E2; Glutathione S transferase (GST1), UGT1-3, 1-7, 2B15, and 2B37; binding cassette transporter (ABC) transporter F family member 4 and ABC transporter G family member 20. Interestingly, there was a significant increase in the expression of the genes such as CYP9E2 (8.3-fold), CYP6A8 (5.9-fold), CYP6D3 (5.4-fold), CYP4C21 (5.4-fold), CYP4G15 (5.2-fold), GST1 (3.5-fold), and ABC transporter 4 (2.1-fold). Our results suggested a potential relationship between the expression of the genes in metabolic processes and insecticide resistance in the studied strain. These results may contribute to the understanding of the mechanisms of insecticide resistance in Ae. aegypti.

Spatial population genomics of a recent mosquito invasion

“…Cytochrome P450 9e2 genes have been linked to insecticide resistance and demonstrated strong upregulation in resistant A . aegypti mosquitoes (Kim Lien et al, 2019). Cytochrome P450 9f2 genes have also been linked to insecticide resistance (Etebari et al, 2018).…”

“…The connectivity of this system also extends beyond borders, with evidence of gene flow from PNG into several of the nearest islands. Some of this gene flow was strongly suggestive of adaptive introgression, specifically at a set of linked outlier SNPs surrounding a genomic region containing 12 cytochrome P450 genes, of types (9e2 and 9f2) previously associated with insecticide resistance (Etebari et al, 2018; Kim Lien et al, 2019). Nonreference alleles at these outlier SNPs were found in four TSI villages, but not in any of the Indonesian populations from which the original invasion was sourced, or any population other than Port Moresby (PNG south coast), indicating a potential cross‐country “genetic invasion” of resistance alleles introgressed from southern PNG to the TSI.…”

Spatial population genomics of a recent mosquito invasion

“…Cytochrome P450 9e2 genes have been linked to insecticide resistance and demonstrated strong upregulation in resistant Ae. aegypti mosquitoes (Kim Lien et al, 2019). Cytochrome P450 9f2 genes have also been linked to insecticide resistance (Etebari et al, 2018).…”

“…The connectivity of this system also extends beyond borders, with evidence of gene flow from PNG into several of the nearest islands. Some of this gene flow was strongly suggestive of adaptive introgression, specifically at a set of linked outlier SNPs surrounding a genomic region containing 12 cytochrome P450 genes, of types (9e2 and 9f2) previously associated with insecticide resistance (Etebari et al, 2018; Kim Lien et al, 2019). Non-reference alleles at these outlier SNPs were found in four TSI villages, but not in any of the Indonesian populations from which the original invasion was sourced, or any population other than Port Moresby (PNG south coast), indicating a potential cross-country ‘genetic invasion’ of resistance alleles introgressed from southern PNG to the TSI.…”

Transcriptomic analysis to elucidate the response of honeybees (Hymenoptera: Apidae) to amitraz treatment

“…However, the function of CYP4C3 has not yet been elucidated in honeybees. A previous study used transcriptome sequencing and bioinformatic analysis to compare transcription levels between a susceptible and resistant strain of Aedes aegypti; it was reported that the expression of genes such as CYP4C3 were significantly upregulated in resistant strain, suggesting the existence of a potential relationship between the expression of genes participating in metabolic processes and insecticide resistance [65]. CarEs include a group of enzymes involved in endocrine control, detoxification, and metabolism of nonpolar carboxyl hydrolases [66][67][68], such as malathion [66], methyl parathion [69], dichlorvos [70], and thiamethoxam [71,72].…”