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Quercetin, one of the most abundant dietary flavonoids, is widely present in nature. In this study, the effects of quercetin ingestion on Helicoverpa armigera larvae growth and its sensitivity to lambda-cyhalothrin were assessed. The median lethal concentration ( LC50) value of lambda-cyhalothrin to quercetin-fed H. armigera larvae was 2.39-fold higher than the control, suggesting a reduced sensitivity to lambda-cyhalothrin. Piperonyl butoxide (PBO) treatment effectively synergized lambda-cyhalothrin efficacy in quercetin-fed H. armigera larvae with a synergistic ratio of 2.36. Moreover, the growth of H. armigera larvae was inhibited by the quercetin uptake. To understand the reduced sensitivity to lambda-cyhalothrin, we measured the enzymatic activity of cytochrome P450 monooxygenases (P450s), as well as transcriptional responses of three P450s genes in quercetin-fed H. armigera larvae. We found that cytochrome P450 monooxygenases involved in the observed lambda-cyhalothrin tolerance in quercetin-fed H. armigera. After fed on quercetin for 48 h, 7-ethoxycoumarin-O-deethylase (ECOD) activity was significantly elevated in quercetin-fed H. armigera larvae; meanwhile, the expression level of CYP6B6, CYP6B8 and CYP321A1 was up-regulated. In conclusion, P450s played a crucial role in the metabolic adaptation of H. armigera larvae to its host plant's secondary metabolites as well as synthetic insecticides. The reduced lambda-cyhalothrin sensitivity in quercetin-fed H. armigera larvae suggested that previous exposure to the host plant-derived quercetin is likely to compromise the efficacy of pyrethroid insecticides. [ABSTRACT FROM AUTHOR]

BACKGROUND: Uridine diphosphate-glucuronosyltransferases (UGTs), as multifunctional detoxification enzymes, play important roles in the biotransformation of various compounds. However, their roles in insecticide resistance are still unclear. This study presents a genome-wide identification of the UGTs in diamondback moth, Plutella xylostella (L.), a notorious insect pest of cruciferous crops worldwide. The possible roles of these UGTs in insecticide resistance were evaluated. RESULTS: A total of 21 putative UGTs in P. xylostella were identified. Quantitative real-time polymerase chain reaction (PCR)-based analyses showed that all the UGT genes were expressed in all tested developmental stages and tissues. Bioassay results indicated that a field-collected population (BL) was resistant to 9 of 10 commonly used insecticides, and 10 of 21 UGT mRNAs were upregulated in the BL population. Exposure to the LC50 of each insecticide affected the expression of most UGT genes. Among these, the expression levels of UGT40V1, UGT45B1 and UGT33AA4 were induced by more than five insecticides, where as in doxacarb and metaflumizone significantly repressed the expression of most UGT genes. CONCLUSION: UGTs may play important roles in the metabolism of commonly used insecticides in P. xylostella. These findings provide valuable information for further research on the physiological and toxicological functions of specific UGT genes in P. xylostella. [ABSTRACT FROM AUTHOR]

Background: Long noncoding RNAs (lncRNAs) are now considered important regulatory factors, with a variety of biological functions in many species including insects. ome lncRNAs have the ability to show rapid responses to diverse stimuli or stress factors and are involved in responses to insecticide. However, there are no reports to date on the characterization of lncRNAs associated with chlorantraniliprole resistance in Plutella xylostella. Results: Nine RNA libraries constructed from one susceptible (CHS) and two chlorantraniliprole-resistant P. xylostella strains (CHR, ZZ) were sequenced, and 1309 lncRNAs were identified, including 877 intergenic lncRNAs, 190 intronic lncRNAs, 76 anti-sense lncRNAs and 166 sense-overlapping lncRNAs. Of the identified lncRNAs, 1059 were novel. Furthermore, we found that 64 lncRNAs were differentially expressed between CHR and CHS and 83 were differentially expressed between ZZ and CHS, of which 22 were differentially expressed in both CHR and ZZ. Most of the differentially expressed lncRNAs were hypothesized to be associated with chlorantraniliprole resistance in P. xylostella. The targets of lncRNAs via cis- (<10 kb upstream and downstream) or trans- (Pearson's correlation, r > 0.9 or < -0.9, P < 0.05) regulatory effects were also identified; many of the differently expressed lncRNAs were correlated with various important protein-coding genes involved in insecticide resistance, such as the ryanodine receptor, uridine diphosphate glucuronosyltransferase (UGTs), cytochrome P450, esterase and the ATP-binding cassette transporter. Conclusions: Our results represent the first global identification of lncRNAs associated with chlorantraniliprole resistance in P. xylostella. These results will facilitate future studies of the regulatory mechanisms of lncRNAs in chlorantraniliprole and other insecticide resistance and in other biological processes in P. xylostella. [ABSTRACT FROM AUTHOR]

The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae) is one of the most serious pests of cruciferous vegetables and has developed resistance to many kinds of insecticides, including abamectin. Abamectin is a neurotoxin that can directly activate or potentiate glutamate-gated chloride channels (GluCls). In the present study, four GluCl variants of P. xylostella (PxGluCl-A, PxGluCl-B, PxGluCl-C and PxGluCl-D) generated by alternative splicing of exons 8, 9 and 10 were identified in a field P. xylostella strain that showed 1389.7-fold resistance to abamectin. Electrophysiological analysis using Xenopus laevis oocytes showed that compared to the original PxGluCl, the PxGluCl-A channel (formed by alternative splicing of exon 8), PxGluCl-B and PxGluCl-C channels (both formed by alternative splicing of exon 9) and PxGluCl-D channel (formed by alternative splicing of exon 10) showed reduced sensitivity to glutamate and abamectin. In addition, the heteromeric channels formed by the combination of the four splice variants also demonstrated significantly reduced sensitivity to glutamate and abamectin except PxGluCl-(B+C), which showed less sensitivity to abamectin but not to glutamate. In contrast, the responses of all the homomeric and heteromeric channels to fipronil were similar to that of the original PxGluCl. These results showed that the expression of four PxGluCl splice variants may be involved in abamectin resistance. Our findings lay a foundation for further investigating the mechanisms of abamectin resistance as well as the physiological functions of these splice variants in insects. [ABSTRACT FROM AUTHOR]

Background: Plant allelochemicals act as toxins, inhibitors of digestion, and deterrents that affect the fecundity of insects. These compounds have attracted significant research attention in recent decades, and much is known about the effects of these xenobiotic plant secondary metabolites on insect development. To date, although ecological interactions between xenobiotic plant secondary chemicals that retard insect growth have been observed in many species, it remains unclear how particular allelochemicals influence insect development in a life stage-dependent manner. Results: We found that 2-tridecanone can affect insect development; this effect appears similar to the symptoms induced by the physiological imbalance between juvenile and molting hormones in cotton bollworm. We later detected that a decrease in the concentration of 20-hydroxyecdysone occurred alongside the observed symptoms. We next identified the transcriptome of Helicoverpa armigera and eightdigital gene expression libraries for shading light on how 2-tridecanone retarded the development of cotton bollworm. The expression of CYP314A1, CYP315A1, CYP18A1, CYP307A1, and CYP306A1 (unigenes 16487, 15409, 40026, 41217, 35643, 16953, 8199, 13311, and 13036) were found to be induced by 2-tridecanone; these are known to be related to the biosynthesis or metabolism of 20-hydroxyecdysone. Expression analysis and RNA interference studies established that the retardant effect of 2-tridecanone on the development of cotton bollworm is mediated by P450 genes. Conclusions: The candidate P450 gene approach described and exploited here is useful for identifying potential causal genes for the influence of plant allelochemicals on insect development. [ABSTRACT FROM AUTHOR]

Propoxur, a carbamate insecticide, has been used worldwide for the control of house flies (Musca domestica L.) for many decades. Resistance levels to propoxur have been detected in field populations of house flies in many parts of the world, including China. In this study, a near-isogenic house fly line (N-PRR) resistant to propoxur was used to determine the mode of inheritance. Bioassay results showed no significant differences in LD50 values or in the slope of log dose-probit lines between the reciprocal F1 and F1' progenies, and the degree of dominance (D) was more than –1 and less than 0. Chi-square analysis of the responses of self-bred (F2, F2') and backcross progenies (BC1, BC2, BC1', and BC2') indicated that a single gene was responsible for resistance. Propoxur resistance in the N-PRR strain of house fly was inherited as a single, major, autosomal, and incompletely recessive factor. These results should be useful to reveal the mode of inheritance and the development trend of propoxur resistance and develop a systematic strategy for the resistance management in house flies. [ABSTRACT FROM AUTHOR]

The green peach aphid, Myzus persicae (Sulzer), is an important insect pest of many crops around the world. Pesticide-induced hormesis may be an alternative mechanism for pest resurgence. In this study, life table parameters were applied to the estimation of sulfoxaflor-induced hormesis of adult M. persicae following 2-d LC25 concentration exposure. Leaf-dip bioassays showed that the sulfoxaflor possessed high toxicity against M. persicae, with an LC50 of 0.059mg/liter. The results indicated that the exposure of the parent generation of M. persicae to sublethal sulfoxaflor induced increase in reproduction and prolongation of immature development duration in the first progeny generation. Both R0 and GRR of aphids for treatment group were significantly higher than for the control in F1 generation, and the mean generation time was significantly postponed in treated group. These results suggest a hormesis induced by lower concentration of sulfoxaflor in M. persicae. It would be useful for assessing the overall effects of sulfoxaflor on M. persicae. [ABSTRACT FROM AUTHOR]

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We identified and characterized the TcLgl gene putatively encoding lethal giant larvae (Lgl) protein from the red flour beetle (Tribolium castaneum). Analyses of developmental stage and tissue-specific expression patterns revealed that TcLgl was constitutively expressed. To examine the role of TcLgl in insect development, RNA interference was performed in early (1-day) larvae, late (20-day) larvae, and early (1-day) pupae. The early larvae injected with double-stranded RNA of TcLgl (dsTcLgl) at 100, 200, and 400 ng/larva failed to pupate, and 100% mortality was achieved within 20 days after the injection or before the pupation. The late larvae injected with dsTcLgl at these doses reduced the pupation rates to only 50.3%, 36.0%, and 18.2%, respectively. The un-pupated larvae gradually died after one week, and visually unaffected pupae failed to emerge into adults and died during the pupal stage. Similarly, when early pupae were injected with dsTcLgl at these doses, the normal eclosion rates were reduced to only 22.5%, 18.0%, and 11.2%, respectively, on day 7 after the injection, and all the adults with abnormal eclosion died in two days after the eclosion. These results indicate that TcLgl plays an essential role in insect development, especially during their metamorphosis. [ABSTRACT FROM AUTHOR]

Background Studies suggest that not only is insecticide resistance conferred via multiple gene upregulation, but it is mediated through the interaction of regulatory factors. However, no regulatory factors in insecticide resistance have yet been identified, and there has been no examination of the regulatory interaction of resistance genes. Our current study generated the first reference transcriptome from the adult house fly and conducted a whole transcriptome analysis for the multiple insecticide resistant strain ALHF (wild-type) and two insecticide susceptible strains: aabys (with morphological recessive markers) and CS (wild type) to gain valuable insights into the gene interaction and complex regulation in insecticide resistance of house flies, Musca domestica. Results Over 56 million reads were used to assemble the adult female M. domestica transcriptome reference and 14488 contigs were generated from the de novo transcriptome assembly. A total of 6159 (43%) of the contigs contained coding regions, among which 1316 genes were identified as being co-up-regulated in ALHF in comparison to both aabys and CS. The majority of these up-regulated genes fell within the SCOP categories of metabolism, general, intra-cellular processes, and regulation, and covered three key detailed function categories: redox detailed function category in metabolism, signal transduction and kinases/phosphatases in regulation, and proteases in intra-cellular processes. The redox group contained detoxification gene superfamilies, including cytochrome P450s, glutathione S-transferases, and esterases. The signal transduction and kinases/phosphatases groups contained gene families of rhodopsin-like GPCRs, adenylate and guanylate cyclases, protein kinases and phosphatases. The proteases group contained genes with digestive, catalytic, and proteinase activities. Genetic linkage analysis with house fly lines comparing different autosomal combinations from ALHF revealed that the up-regulation of gene expression in the three key SCOP detailed function categories occurred mainly through the co-regulation of factors among multiple autosomes, especially between autosomes 2 and 5, suggesting that signaling transduction cascades controlled by GPCRs, protein kinase/phosphates and proteases may be involved in the regulation of resistance P450 gene regulation. Conclusion Taken together, our findings suggested that not only is insecticide resistance conferred via multi-resistance mechanisms or up-regulated genes, but it is mediated through the trans and/or cis co-regulations of resistance genes. [ABSTRACT FROM AUTHOR]

The cytochrome P450 s play a significant role in the detoxification of plant allelochemicals and synthetic insecticides in Lepidoptera. In the cotton bollworm Helicoverpa armigera, 2-tridecanone and quercetin can induce P450-dependent monooxygenase activity increased, to further the characterization of P450, the CYP6B6 of cotton bollworm ( H. armigera) was cloned, sequenced and expressed in pMAL-p2x vector and expressed in Escherichia coli. The deduced amino acid sequences of cytochrome P450 in the midgut and fat body of H. armigera showed 98.23 and 97.84 % similarity with CYP6B6, respectively. According to nomenclature of P450 s, the P450 genes we got belong to CYP6B. Purification of recombinant protein based on the affinity of MBP for maltose was achieved by Mal-Tag magnetic beads. The purified protein was used to raise polyclonal antibody according to classical procedure. SDS-PAGE and Western blot results indicated that MBP-CYP6B6 had been successfully expressed. The ethoxycoumarin-O-deethylase activity of the purified recombinant protein was 36.5 ± 8.12 pmol of 7-hydroxycoumarin/min/mg protein, which showed the fusion MBP-CYP6B6 had the ability to o-deethylase of 7-ethoxycoumarin. [ABSTRACT FROM AUTHOR]

Background: The diamondback moth, Plutella xylostella (L.) (Lepidoptera: Plutellidae), is a devastating pest of cruciferous crops worldwide, and has developed resistance to a wide range of insecticides, including diacylhydrazine-based ecdysone agonists, a highly selective group of molt-accelerating biopesticides targeting the ecdysone receptors. Result: In this study, we cloned and characterized the ecdysone receptors from P. xylostella, including the two isoforms of EcR and a USP. Sequence comparison and phylogenetic analysis showed striking conservations among insect ecdysone receptors, especially between P. xylostella and other lepidopterans. The binding affinity of ecdysteroids to in vitro-translated receptor proteins indicated that PxEcRB isoform bound specifically to ponasterone A, and the binding affinity was enhanced by co-incubation with PxUSP (Kd =3.0±1.7 nM). In contrast, PxEcRA did not bind to ponasterone A, even in the presence of PxUSP. The expression of PxEcRB were consistently higher than that of PxEcRA across each and every developmental stage, while the pattern of PxUSP expression is more or less ubiquitous. Conclusions: Target site insensitivity, in which the altered binding of insecticides (ecdysone agonists) to their targets (ecdysone receptors) leads to an adaptive response (resistance), is one of the underlying mechanisms of diacylhydrazine resistance. Given the distinct differences at expression level and the ligand-binding capacity, we hypothesis that PxEcRB is the ecdysone receptor that controls the remodeling events during metamorphosis. More importantly, PxEcRB is the potential target site which is modified in the ecdysone agonist-resistant P. xylostella. [ABSTRACT FROM AUTHOR]

Since the report of a paralogous acetylcholinesterase (AChE, EC3.1.1.7) gene in the greenbug (Schizaphis graminum) in 2002, two different AChE genes (Ace1 and Ace2) have been identified in each of at least 27 insect species. However, the gene models of Ace1 and Ace2, and their molecular properties have not yet been comprehensively analyzed in any insect species. In this study, we sequenced the full-length cDNAs, computationally predicted the corresponding three-dimensional protein models, and profiled developmental stage and tissue-specific expression patterns of two Ace genes from the red flour beetle (Tribolium castaneum; TcAce1 and TcAce2), a globally distributed major pest of stored grain products and an emerging model organism. TcAce1 and TcAce2 encode 648 and 604 amino acid residues, respectively, and have conserved motifs including a choline-binding site, a catalytic triad, and an acyl pocket. Phylogenetic analysis show that both TcAce genes are grouped into two insect Ace clusters and TcAce1 is completely diverged from TcAce2, suggesting that these two genes evolve from their corresponding Ace gene lineages in insect species. In addition, TcAce1 is located on chromosome 5, whereas TcAce2 is located on chromosome 2. Reverse transcription polymerase chain reaction (PCR) and quantitative realtime PCR analyses indicate that both genes are virtually transcribed in all the developmental stages and predominately expressed in the insect brain. Our computational analyses suggest that the TcAce1 protein is a robust acetylcholine (ACh) hydrolase and has susceptibility to sulfhydryl agents whereas the TcAce2 protein is not a catalytically efficient ACh hydrolase. [ABSTRACT FROM AUTHOR]

Spinosad, a relatively new, effective and safe pesticide, has been widely used in pest control over the last 10 years. However, different levels of resistance to this insecticide have developed in some insects worldwide. After continuous selection for 27 generations, a strain (SpRR) of the housefly developed 247-fold resistance to spinosad compared with the laboratory susceptible strain (CSS). The estimated realised heritability ( h) of spinosad resistance was 0.14. There was no significant difference in the LD values and slopes between reciprocal progenies F and F′, and values of 0.33 (F) and 0.30 (F′) were obtained for the degree of dominance. Chi-square analysis from responses of self-bred (F) and backcrosses (BC and BC) were highly significant, suggesting that the resistance was probably controlled by more than one gene. Synergists piperonyl butoxide (PBO), diethyl maleate (DEM) and S, S, S-tributyl phosphorotrithioate (DEF) affected the toxicity of spinosad at a low level, and demonstrated that metabolic-mediated detoxification was not an important factor in conferring resistance to spinosad in the SpRR strain. It was concluded that spinosad resistance in the housefly was autosomal and incompletely dominant, and the resistance was probably controlled by more than one gene. These results provide the basic information for designing successful management programmes for the control of houseflies. Copyright © 2011 Society of Chemical Industry [ABSTRACT FROM AUTHOR]

Microplitis mediator Haliday (Hymenoptera: Braconidae) is an important larval endoparasitoid of various lepidopteran pests, including Helicoverpa armigera (Hübner). In China, H. annigera is a key pest of cotton and is currently the focus of several biological control efforts that use M. mediator as principal natural enemy of this pest. To improve the success of biological control efforts, behavioral studies are needed that shed light on the interaction between M. mediator and H. armigera. In this study, we determined M. mediator response to volatile compounds from undamaged, mechanically injured, or H. armigera--damaged plants and identified attractive volatiles. In Y-tube olfactometer assays, we found that mechanically damaged plants and/or plants treated with H. arinigera oral secretions did not attract wasps. However, volatiles from H. armigeradamaged plants elicited a strong attraction of both M. mediator sexes. Headspace extracts from H. armigera-damaged cotton were analyzed by coupled gas chromatographyelectroantennographic detection (GC-EAD), and a total of seven different compounds were found to elicit electroantennogram (EAG) responses, including an unknown compound. Six different EAD-active volatiles were identified from caterpillar-damaged cotton plants, of which 3, 7-dimethyl-1, 3, 6-octatriene and (Z)-3-hexenyl acetate were the principal compounds. Olfactometer assays indicated that individual synthetic compounds of 3, 7-dimethyl-1, 3, 6-octatriene, (Z) -3-hexenyl acetate, and nonanal were attractive to M. mediator. Field cage studies showed that parasitism of H. armigera larvae by M. mediator was higher on cotton plants to which 3,7-dimethyl-1,3, 6-octatriene was applied. Our results show that the combination of terpenoids and green leaf volatiles may not only facilitate host, mate, or food location but may also increase H. armigera parasitism by M. mediator. [ABSTRACT FROM AUTHOR]

The article presents a study on the mode of inheritance of resistance to fufenozide in a laboratory-selected colony of diamondback moth (DBM). The fufenozide was given by Jiangsu Pesticide Research Institute, China while the susceptible strain of DBM came from Professor Han Zhaojun of Nanjing Agricultural University. The tests revealed that the resistance to fufenozide in DBM was autosomally inherited and completely recessive. It suggests that target-size resistance rather than metabolic resistance plays an important role in fufenozide resistance in DBM.

In this study, the acute toxicity of the pesticide methomyl on the topmouth gudgeon ( Pseudorasbora parva) was evaluated using mortality and the activity of the enzymes acetylcholinesterase (AChE), glutathione S-transferases (GSTs), glutamic oxaloacetic transaminase (GOT) and glutamic pyruvic transaminase (GPT) as endpoints. LC50 values were 1.228, 0.782, 0.538, and 0.425 mg/l at 24, 48, 72, and 96 h of exposure, respectively. Methomyl caused a sharp decrease in specific activity of brain AChE around 48% at concentrations between 0.043 and 0.213 mg/l. A reduction higher than 40% in liver GST activity at concentrations between 0.085 and 0.213 mg/l was found, whereas no significant effects were observed in intestinal GST. A significant concentration-dependent decrease of GOT activity was found after 24 h of exposure to the pesticide but not after 96 h. No significant effects on GPT activity were observed. These results indicate that at the concentrations tested, methomyl is acutely toxic to the species P. parva, causing mortality, neurotoxic effects, and changes in some hepatic enzymes. [ABSTRACT FROM AUTHOR]

The article presents a study which examines the mode of inheritance of beta-cypermethrin resistance in the housefly Musca domestica. The result shows that the estimated realized heritability of beta-cypermethrin resistance was 0.30. Chi-square analysis from responses of self-bred and backcross progenies was used to test if a single gene is responsible for resistance. The study concludes that beta-cypermethrin resistance in the housefly was inherited as a single, major, autosomal and incompletely recessive factor.

The substrate specificity of brain acetylcholinesterase (AChE) in adult Carassius auratus fish and its sensitivity to carbamate insecticides were investigated in vitro. The results showed that the order of four substrates hydrolyzed by brain AChE in C. auratus was acetylthiocholine iodide > β-methylthiocholine iodide > propionylthiocholine iodide > butyrylthiocholine iodide, and the maximum velocity ( V max) of AChE hydrolyzing acetylthiocholine iodide (ATCh) was the highest among the four substrates, and the V max values were 0.067 and 0.082 mmol min−1 mg−1 for male and female fish respectively. But their Michaelis–Menten constants ( K m) were the lowest, only 0.071 and 0.072 mmol/l respectively. Compared with other carbamate insecticides, the sensitivity of brain AChE to carbofuran was the highest and the IC50 values were 1.04 × 10−6 mol/l for females and 1.17 × 10−6 mol/l for males. The inhibitory tendencies of eserine, methomyl, and aldicarb to brain AChE were very similar, and the percentage inhibition increased with time at the concentration of 1 × 10−6 mol/l. The order of inhibition potential of the three inhibitors from the highest to the lowest was eserine, aldicarb, and methomyl. [ABSTRACT FROM AUTHOR]

In this article we review the use of medicinal insects in China. We briefly describe the history of medicinal insect use, current resources of medicinal insects, and the various forms in which medicinal insects are consumed. The current research situation of medicinal insectresearch is discussed, as well as its future prospects. [ABSTRACT FROM AUTHOR]

Carboxylesterases (CarEs) are one of the major enzyme families associated with the detoxification of estercontaining xenobiotics including insecticides. The contribution of CarEs to single insecticide resistance have been reported widely. However, little is known about the roles of CarEs in multi-insecticide resistance. In this study, a total of 46 genes were identified in CarE family of Plutella xylostella (L.), a notorious pest of cruciferous crops, of which 21 genes were found overexpressed in field collected Hainan (HN) and Guangdong (GD) populations which showed moderate to extremely high resistance to beta-cypermethrin, chlorantraniliprole, metaflumizone, phoxim and tebufenozide. Among the 21 overexpressed CarE genes, PxaE3, PxaE6, PxaE9, PxaE13 and PxaE27 can be upregulated significantly by LC25 of the five insecticides. Knockdown of the five genes by RNA interference and the followed bioassays revealed that PxaE3 was involved in chlorantraniliprole resistance, PxaE6, PxaE9 and PxaE13 to phoxim resistance, PxaE9 and PxaE27 to betacypermethrin resistance, respectively. The bioassay results with transgenic fruit flies overexpressing each of the five genes confirmed their roles in resistance to the three insecticides. Our results demonstrated that at least five carboxylesterase genes were involved in multi-insecticide resistance in P. xylostella through constitutive and inductive overexpression, and provided foundations for further understanding the molecular mechanisms of multi-insecticide resistance in pest insects. [ABSTRACT FROM AUTHOR]

Ecdysone receptor (EcR) plays important roles in molting, metamorphosis, and reproduction of insects. EcR ortholog and its function in melon aphid Aphis gossypii have not been documented yet. RNA interference (RNAi) is a reverse-genetic approach used to study functional genomics, but recently, it has also shown promise as a novel tool that could be used to control insect pests. In this study, reverse transcription-PCR (RT-PCR), quantitative real-time PCR (qPCR), RNAi, and bioassays were employed to isolate EcR gene and investigate its knock-down effects on aphids. The lethal and sublethal effects were also studied after silencing the EcR gene. The results showed that EcR gene is highly expressed (P < 0.006) in 2nd nymphal stage of A. gossypii while expression was statistically lower in all other developmental stages. Knock-down of EcR gene caused up to 43 and 68% mortality in 2nd instar nymphs after feeding dsEcR for 48 and 72 h, respectively, compared to the control. Moreover, RNAi-induced silencing of EcR gene caused sublethal effects on surviving aphids. Significantly lower longevity (about 42%) and fecundity (about 44.22%) were observed in insects fed with dsEcR solution at their nymphal stage. Analysis of gene expression showed that the mortality rates and the lowered longevity and fecundity were attributable to the down-regulation of EcR gene by RNA interference technology. Taken together, our results demonstrate that EcR is an essential gene for aphid growth and development and could be a potential target gene for the development of an RNAi-based bio-aphicide. [ABSTRACT FROM AUTHOR]

The diamondback moth (DBM), Plutella xylostella (L.), is a serious pest that feeds on cruciferous crops. Prolonged exposure to insecticides has led to increased resistance and biological fitness alterations, such as reduced sensitivity to pheromones. However, the mechanisms underlying the influence of insecticides on sex pheromone recognition in male moths have not been elucidated. In this study, we found that male adults from the NIL strain (a chlorantraniliproleresistant strain) showed decreased responses to sex pheromones at both the behavioral and electrophysiological levels compared to the SS strain (a susceptible strain) and the relative expression of the two pheromone-binding protein (PBP) genes (PxPBP1 and PxPBP2) was downregulated in NIL compared to SS. Furthermore, downregulation of PxPBP1 and PxPBP2 by RNAi inhibited the responses of male moths to the sex pheromone at both the electrophysiological and behavioral levels. Fluorescence binding assays, homology modeling and molecular docking indicated that chlorantraniliprole could robustly bind both PxPBP1 and PxPBP2. The results indicated that the development of resistance to chlorantraniliprole reduced the response of DBM males to sex pheromones through the binding and downregulation of PxPBP1 and PxPBP2. This work provides new evidence for understanding the trade-offs between insecticide resistance and chemical communication as well as the fitness cost of insecticide resistance, in insects. [ABSTRACT FROM AUTHOR]

Although the bird cherry-oat aphid, Rhopalosiphum padi (L.) (Homoptera: Aphididae), is an important grain pest, has developed resistance against various insecticides, information on its reference database remains scarce. In the present study, imidacloprid-resistant strain of R. padi (ImR) displayed a 27.12-fold resistance to imidacloprid compared to the susceptible R. padi strain (SS). We used single-molecule real-time (SMRT) sequencing on PacBio platform and next generation sequencing on the Illumina HiSeq platform to obtain the R. padi transcriptome. Using SMRT sequencing, we obtained 9.36 Gb of clean data with 36,064 unique SMRT transcripts, of which 33,713 were annotated. We then predicted 28,556 complete CDS regions and 2,361 LncRNAs. There were 327 (194 upregulated, 133 downregulated), 272 (181 upregulated, 91 downregulated), and 512 (325 upregulated, 187 downregulated) DETs in the 3 transcript groups designated as "SS vs ImR", "SS Control vs SS IMI(imidacloprid-treated)", and "ImR Control vs ImR IMI", respectively. The DETs of 3 groups were classified according to the GO, COG and KEGG pathway databases and some of them were enriched. The relative expression of 20 randomly selected DETs, was evaluated by quantitative real-time PCR. The observed transcriptional trend matched that observed for DESeq expression profiles. The present study is the first to use SMRT and NGS platforms for transcriptome sequencing and determining the mechanism driving insecticide resistance in R. padi. The fulllength sequencing of the R. padi transcriptome will provide a reference for molecular studies examining other physiological and biochemical mechanisms. [ABSTRACT FROM AUTHOR]

RNA interference (RNAi) has been proved to be a viable method for agricultural pest control. Due to the limited uptake of dsRNA in hemiptera insects, this study used nanocarrier SPc (star polycation) transdermal delivery systems to deliver two truncated fragments (P1/P2) dsRNA of the CYP6CY3 for silencing this target gene in Aphis gossypii. After the cotton aphid was sprayed with the SPc + dsP1/P2 mixture, the expression level of target gene in SPc + dsP1 treatment group was not different from that in dsP1 group at 24 h, 48 h, and significantly lower than that in dsP1 group at 60 h, 72 h, respectively; and the expression level of target gene in SPc + dsP2 treatment group was not different from that in dsP2 group at 24 h, and significantly lower than that in dsP2 group from 48 h, 60 h, 72 h, respectively. In addition, the expression level was continuously silenced after spraying the SPc + dsP1/P2 mixture and significant reduced by 79.7% and 84.3% at 48 h compared with the H 2 O control group, the mortality rate reached 48.09% and 43.18% at 84 h, respectively. And the cumulative reproduction number of cotton aphids also decreased, but the cumulative death number of newborn nymphs had an increase trend, compared with the control groups. Bioassays after RNAi showed that the silencing of CYP6CY3 increased the susceptibility of the 4th instar aphid to imidacloprid, and increased mortality by 67.21% and 58.69% at 96 h, respectively. The life table parameters of the offspring from the 4th instar cotton aphids from the SPc + dsP1/P2 treatment groups showed that the offspring had a longer pre-reproductive period and post-reproductive period. The intrinsic growth rate was 0.231 ± 0.005, 0.210 ± 0.013 and the finite growth rate was 1.260 ± 0.007 and 1.234 ± 0.016 in the SPc + dsP1/P2 treatment group, these two parameters of the two groups were lower than that of the corresponding control，the population doubling time of the two groups was prolonged and the developmental duration was delayed. These results indicate that CYP6CY3 plays a key role in the growth, development, reproduction and detoxification ability in cotton aphids, and may be as a potential RNAi target for controlling aphids, laying the foundation for the development of new environmentally-friendly RNA pesticides in this field. [Display omitted] • Effect of CYP6CY3 silencing on A. gossypii by using nanocarrier transdermal delivery system. • Silencing of CYP6CY3 reduced the survival and reproductive capacity of A. gossypii. • Silencing of CYP6CY3 increased the sensitivity of A. gossypii to imidacloprid. • The offspring life parameters of A. gossypii declined after CYP6CY3 gene silencing. [ABSTRACT FROM AUTHOR]