Multiple P450s and Variation in Neuronal Genes Underpins the Response to the Insecticide Imidacloprid in a Population ofDrosophila melanogaster

Abstract

Abstract:Insecticide resistance is an economically important example of evolution in response to intense selection pressure. Here, the genetics of resistance to the neonicotinoid insecticide imidacloprid is explored using the Drosophila Genetic Reference Panel, a collection of inbred Drosophila melanogaster genotypes derived from a single population in North Carolina. Imidacloprid resistance varied substantially among genotypes, and more resistant genotypes tended to show increased capacity to metabolize and excrete imidacloprid. Variation in resistance level was then associated with genomic and transcriptomic variation, implicating several candidate genes involved in central nervous system function and the cytochrome P450s Cyp6g1 and Cyp6g2. CRISPR-Cas9 mediated removal of Cyp6g1 suggested that it contributed to imidacloprid resistance only in backgrounds where it was already highly expressed. Cyp6g2, previously implicated in juvenile hormone synthesis via expression in the ring gland, was shown to be expressed in metabolically relevant tissues of resistant genotypes. Cyp6g2 overexpression was shown to both metabolize imidacloprid and confer resistance. These data collectively suggest that imidacloprid resistance is influenced by a variety of previously known and unknown genetic factors.

The spread of resistance to imidacloprid is restricted by thermotolerance in natural populations of Drosophila melanogaster

“…Conversely, we only identified two genes belonging to the canonical detoxification genes family, and neither of these (Cyp311a1 and Cyp4s3) are strong candidates for having roles in insecticide metabolism. The P450 Cyp6g1, that has previously been associated with imidacloprid metabolism [62][63][64] , was not detected in our analysis and inspection of a SNP tagging the CNV believed to be causal for the resistance (2R:12185332), is fixed in almost all Australian populations (the exception being a South Australian population) and was at high frequency in the north American populations we sampled (0.71 to 0.97). The analysis of microbial "hologenomes" adds another likely contributor to the multifactorial basis to variation in insecticide mortality.…”

Comparative CYP‐omic analysis between the DDT‐susceptible and ‐resistant Drosophila melanogaster strains 91‐C and 91‐R

“…33 Most recently, two P450s, Cyp6g1 and Cyp6g2, have been shown to contribute to the metabolization of imidacloprid and are involved in conferring resistance to this insecticide in D. melanogaster. 34 Additionally, multiple P450s associated with DDT resistance were over-transcribed in the highly DDT-resistant D. melanogaster strain as compared to DDT-susceptible strain, suggesting that resistance may be in part attributable to differential expression of multiple P450s. 35,36 Retention of a functional Nrf2/Maf (NF-E2-related factor 2/Muscle aponeurosis fibromatosis) transcription factor binding site was previously linked to the over-expression of Cyp6a2 associated with DDT resistance in 91-R, 37 as was trans-regulatory control by the D. melanogaster CNC-bZIP (Cap'n'collar-basic leucine zipper) transcription factor ortholog to Nrf2 that regulates the transcriptional response of several genes encoding detoxification enzymes that contain an upstream antioxidant response element (ARE), 38,39 including Cyp6a2 and Cyp6a8.…”

“…has also shown that Cyp6g1 is involved in organophosphate resistance through transgenically overexpressing the Accord element from a resistant strain (Hikone‐R) in D. melanogaster . Most recently, two P450s, Cyp6g1 and Cyp6g2 , have been shown to contribute to the metabolization of imidacloprid and are involved in conferring resistance to this insecticide in D. melanogaster …”

Signatures of insecticide selection in the genome of Drosophila melanogaster

“…2016; Schmidt et al . 2017; Denecke et al . 2017), but have not yet been used to evaluate resistance to insecticides that have been and continue to be widely used, such as pyrethroids.…”