Molecular Cloning, Expression Pattern and Polymorphisms of NADPH-Cytochrome P450 Reductase in the Bird Cherry-Oat Aphid Rhopalosiphum padi (L.)

Abstract

NADPH–cytochrome P450 reductase (CPR) plays an important role in the cytochrome P450 (CYP)-mediated metabolism of endogenous and exogenous substrates. CPR has been found to be associated with insecticide metabolism and resistance in many insects. However, information regarding CPR in the bird cherry-oat aphid, Rhopalosiphum padi, is unavailable. In the current study, a full-length cDNA (2,476 bp) of CPR (RpCPR) encoding 681 amino acids was cloned from R. padi. Nucleotide sequence and deduced amino acid sequence analysis showed that RpCPR exhibits characteristics of classical CPRs and shares high identities with those of other insects, especially with the pea aphid, Acyrthosiphon pisum. The mRNA of RpCPR was expressed at all developmental stages, with the highest expression level found in the second instar and the lowest in adult. Expression levels of RpCPR in isoprocarb-resistant and imidacloprid-resistant strains were 3.74- and 3.53-fold higher, respectively, than that of a susceptible strain. RpCPR expression could also be induced by low concentrations (LC30) of isoprocarb and imidacloprid. Moreover, we sequenced the open reading frame (ORF) of RpCPR from 167 field samples collected in 11 geographical populations. Three hundred and thirty-four SNPs were detected, of which, 65 were found in more than two individuals. One hundred and ninety-four missense mutations were present in the amino acid sequence, of which, the P484S mutant had an allele frequency of 35.1%. The present results suggest that RpCPR may play an important role in the P450-mediated insecticide resistance of R. padi to isoprocarb and imidacloprid and possibly other insecticides. Meanwhile, RpCPRmaintains high genetic diversity in natural individuals, which provides the possibility of studying potential correlations between variants and certain special physiological characters.

Characterisation of imidacloprid resistance in the bird cherry‐oat aphid, Rhopalosiphum padi, a serious pest on wheat crops

“…It was reported that a bioassay method that combined direct contact with an insecticide and subsequent exposure to residues on leaves gave a measurable resistance factor in the determination of resistance of M. persicae to neonicotinoids, while the resistance level could not be measured because of insufficient mortality at the highest concentration when using a bioassay method that applied the insecticide directly to the dorsal surface of individual aphids . We adopted a leaf‐dipping bioassay method that combined direct contact and residue exposure for the insects in this study . Stocks of insecticides were prepared in acetone (10 g L ‐1 ) and diluted in a series of concentrations containing 0.01% (v/v) Triton X‐100 for bioassays.…”

“…9 We adopted a leaf-dipping bioassay method that combined direct contact and residue exposure for the insects in this study. 5 Stocks of insecticides were prepared in acetone (10 g L -1 ) and diluted in a series of concentrations containing 0.01% (v/v) Triton X-100 for bioassays. Wheat leaves with apterous adult aphids were dipped into insecticide solutions for 10 s, and the residual droplets of the solution on the leaves were absorbed by dry filter paper.…”

“…Aside from direct feeding damage, R. padi also transmits the barley yellow dwarf virus (BYDV), which causes an economically important disease in small grains, leading to reduced quality and yield . In recent years, outbreaks of this pest have often occurred in China, and it has shown an increasing degree of resistance to some insecticides, including organophosphates and carbamates . Since its introduction in the early 1990s, imidacloprid has rapidly become one of the most commonly used neonicotinoid insecticides against aphids, whiteflies, and planthoppers .…”

“…2 In recent years, outbreaks of this pest have often occurred in China, 3,4 and it has shown an increasing degree of resistance to some insecticides, including organophosphates and carbamates. [5][6][7] Since its introduction in the early 1990s, imidacloprid has rapidly become one of the most commonly used neonicotinoid insecticides against aphids, whiteflies, and planthoppers. 8 Regional susceptibility analyses of 12 R. padi field populations showed that some populations had different resistance levels to imidacloprid, with the highest resistance ratio being 13.6; however, the resistance levels of Myzus persicae and Aphis gossypii field populations to imidacloprid were much higher.…”

Peer Review #1 of "Asexual reproduction of a few genotypes favored the invasion of the cereal aphid Rhopalosiphum padi in Chile (v0.1)"

“…padi, insecticide-resistant samples from China have been recently described (Wang et al, 2016(Wang et al, , 2018. However, it remains unknown whether these strains correspond to clonal lineages developing as superclones.…”