Overexpression of a cytochrome P450 and a UDP-glycosyltransferase is associated with imidacloprid resistance in the Colorado potato beetle, Leptinotarsa decemlineata

Abstract

Current control of insect pests relies on chemical insecticides, however, insecticide resistance development by pests is a growing concern in pest management. The main mechanisms for insecticide resistance typically involve elevated activity of detoxifying enzymes and xenobiotic transporters that break-down and excrete insecticide molecules. In this study, we investigated the molecular mechanisms of imidacloprid resistance in the Colorado potato beetle, Leptinotarsa decemlineata (Say) (Coleoptera: Chrysomelidae), an insect pest notorious for its capacity to develop insecticide resistance rapidly. We compared the transcriptome profiles of imidacloprid-resistant and sensitive beetle strains and identified 102 differentially expressed transcripts encoding detoxifying enzymes and xenobiotic transporters. Of these, 74 were up-regulated and 28 were down-regulated in the resistant strain. We then used RNA interference to knock down the transcript levels of seven up-regulated genes in the resistant beetles. Ingestion of double-stranded RNA successfully knocked down the expression of the genes for three cytochrome P450s (CYP6BQ15, CYP4Q3 and CYP4Q7), one ATP binding cassette (ABC) transporter (ABC-G), one esterase (EST1), and two UDP-glycosyltransferases (UGT1 and UGT2). Further, we demonstrated that silencing of CYP4Q3 and UGT2 significantly increased susceptibility of resistant beetles to imidacloprid, indicating that overexpression of these two genes contributes to imidacloprid resistance in this resistant strain.

Identification of glutathione S‐transferases in Bemisia tabaci (Hemiptera: Aleyrodidae) and evidence that GSTd7 helps explain the difference in insecticide susceptibility between B. tabaci Middle East‐Minor Asia 1 and Mediterranean

“…LdGST-e2a, LdGST-e2b, LdGST-o5 and LdGST-t1 were significantly overexpressed in Leptinotarsa decemlineata after exposure to the insecticides fipronil, endosulfan or cyhalothrin (Han et al, 2016). In addition, there are many papers about the mechanism of resistance to imidacloprid that indicate that P450s are involved in this mechanism (Karunker et al, 2008;Bao et al, 2016;Pang et al, 2016;Zhang et al, 2016;Kaplanoglu et al, 2017). For example, a P450 gene (CYP6ER1) was found to be associated with imidacloprid resistance in N. lugens (Pang et al, 2016); Similarly, CYP6CM1 was found to be important in imidacloprid resistance in both B. tabaci MED and MEAM1 (Karunker et al, 2008).…”

Identification of a novel cytochrome P450 CYP3356A1 linked with insecticide detoxification in Bradysia odoriphaga

“…[5][6][7][8] More importantly, transcriptional overexpression of P450 genes and the corresponding enhanced metabolic ability are often found in insecticide-resistant populations, and this appears to be a common phenomenon in the evolution of resistance. [9][10][11][12] For example, overexpression of CYP4Q3 contributes to imidacloprid resistance in a Colorado potato beetle Leptinotarsa decemlineata resistant strain, 13 and overexpression of cytochrome P450 CYP6CM1 is linked to high resistance to imidacloprid in the B and Q biotypes of Bemisia tabaci (Hemiptera: Aleyrodidae). 14 Expression of CYP9M10 was 260-fold higher in a permethrin-resistant Culex quinquefasciatus strain, compared with the susceptible strain.…”

Overexpression of UDP‐glycosyltransferase potentially involved in insecticide resistance in Aphis gossypii Glover collected from Bt cotton fields in China

“…In insect, UGTs commonly catalyze conjugation of small lipophilic substrates with UDP‐glucose, playing an important role in detoxification and homeostatic function . The overexpression of UGT genes in insecticide‐resistant insects has been reported in Leptinotarsa decemlineata (Say), Plutella xylostella (L.) Diaphorina citri Kuwayama, Tetranychus cinnabarinus (Boisduval), and Anopheles sinensis Wiedemann . It has been reported that UGTs were induced by insecticide exposures in Spodoptera exigua (Hübner) and Bemisia tabaci (Gennadius) …”

“…11,12 The overexpression of UGT genes in insecticide-resistant insects has been reported in Leptinotarsa decemlineata (Say), Plutella xylostella (L.) Diaphorina citri Kuwayama, Tetranychus cinnabarinus (Boisduval), and Anopheles sinensis Wiedemann. [13][14][15][16][17] It has been reported that UGTs were induced by insecticide exposures in Spodoptera exigua (Hübner) and Bemisia tabaci (Gennadius). 18,19 www.soci.org X Chen et al…”