Characterization of Insecticide Response-Associated Transcripts in the Colorado Potato Beetle: Relevance of Selected Cytochrome P450s and Clothianidin

Abstract

The Colorado potato beetle (Leptinotarsa decemlineata (Say)) is known for its capacity to cause significant damages to potato crops worldwide. Multiple approaches have been considered to limit its spread including the use of a diverse arsenal of insecticides. Unfortunately, this insect frequently develops resistance towards these compounds. Investigating the molecular bases underlying the response of L. decemlineata against insecticides is of strong interest to ultimately devise novel and targeted approaches aimed at this pest. This work aimed to characterize, via qRT-PCR, the expression status of targets with relevance to insecticide response, including ones coding for cytochrome P450s, glutathione s-transferases, and cuticular proteins, in L. decemlineata exposed to four insecticides; chlorantraniliprole, clothianidin, imidacloprid, and spinosad. Modulation of levels associated with transcripts coding for selected cytochrome P450s was reported in insects treated with three of the four insecticides studied. Clothianidin treatment yielded the most variations in transcript levels, leading to significant changes in transcripts coding for CYP4c1, CYP4g15, CYP6a13, CYP9e2, GST, and GST-1-Like. Injection of dsRNA targeting CYP4c1 and CYP9e2 was associated with a substantial decrease in expression levels and was, in the case of the latter target, linked to a greater susceptibility of L. decemlineata towards this neonicotinoid, supporting a potential role for this target in clothianidin response. Overall, this data further highlights the differential expression of transcripts with potential relevance in insecticide response, as well as generating specific targets that warrant investigation as novel dsRNA-based approaches are developed against this insect pest.

Role of CYP9E2 and a long non-coding RNA gene in resistance to a spinosad insecticide in the Colorado potato beetle, Leptinotarsa decemlineata

“…Of the two upregulated CYPs, we were able to confirm upregulation of CYP9E2 in both field populations compared with SLP; and in OFP, which has the highest resistance to spinosad, the CYP9E2 gene had the greatest transcript level increase. Interestingly, CYP9E2 was also previously shown to be constitutively overexpressed in a New York population of CPB with overall reduced baseline sensitivity to multiple insecticides, including spinosad [68], and knock-down of this gene resulted in increased susceptibility to the neonicotinoid insecticide clothianidin [69]. Also, CYP9E2 transcript levels were elevated in another CPB population upon spinosad exposure [29,30].…”

Expression and Functional Analysis of Two Cytochrome P450 Monooxygenase Genes and a UDP-Glycosyltransferase Gene Linked with Thiamethoxam Resistance in Colorado Potato Beetle

“…Our study showed that thiamethoxam exposure significantly increased expression of the three genes in URMQY adults. Similarly, the transcript level of CYP9e2 increased 4.2-fold in L. decemlineata exposed to clothianidin [30]. In addition, CYP9e2-like genes are involved in insect resistance to a variety of insecticides.…”

“…The roles of CYP9e2-like genes in insecticide resistance of insects have also been reported. Bouafoura et al [30] found that CYP9e2 knockdown increased the susceptibility of L. decemlineata to clothianidin. A cytochrome P450, CYP9E2 and a long non-coding RNA gene lncRNA-2 were found upregulated spinosad resistant population of CPB and Knock-down of these two genes using RNAi resulted in a significant increase of spinosad sensitivity, which imply CYP9E2 and lncRNA-2 jointly contribute to spinosad resistance [38].…”

Leveraging RNA Interference to Impact Insecticide Resistance in the Colorado Potato Beetle, Leptinotarsa decemlineata

“…In addition to studies showcasing a potential role for cytochrome P450s in imidacloprid response, it is noteworthy to point out that knockdown of CYP350D1 via double-stranded RNA (dsRNA) injection in adult L. decemlineata was associated with a positive impact on chlorantraniliprole response [ 35 ]. Another study demonstrated changes in transcripts coding for CYP4C1 , CYP4G15 , CYP6A13 , and CYP9E2 following clothianidin treatment in L. decemlineata , and the injection of dsRNA targeting CYP9E2 was associated with increased susceptibility towards this compound [ 36 ]. It is interesting to note that parallel work identified structural variants in CYP4g15 as notably exemplified by the significant number of single nucleotide polymorphism outliers associated with this target and suggested a potential contribution of this candidate cytochrome P450 in insecticide resistance [ 37 ].…”