Abstract N6-methyladenosine (m 6 A) modification is the most predominant and ubiquitous internal modification of RNA in eukaryotes, serving as a key post-transcriptional regulator of gene expression that is dynamically modulated by methyltransferases (writers) and demethylases (erasers). However, while the functions of m 6 A methylases have been partially elucidated in insects, the identity of m 6 A erasers in arthropods and their chemical catalytic mechanisms, as well as biological functions, remains largely enigmatic. Here, we uncovered 2499 putative methylase genes and 1148 putative demethylase genes in 266 insect genomes, and demonstrated that ALKBH4 functions as an m 6 A demethylase in the whitefly, Bemisia tabaci , catalyzing the oxidative reversal of mRNA m 6 A modifications both in vitro and in vivo. Furthermore, we established that ALKBH4, in coordination with other core components of the m 6 A pathway, fulfills an essential function in regulating the transcript stability of Imaginal Disk Growth Factor 1 (IDGF1) during whitefly development. Collectively, our findings expand the evolutionary scope of the eukaryotic m 6 A modification system, and reveal a conserved yet insect-specific epitranscriptomic regulatory mechanism governing fundamental physiological processes and adaptive phenotypes. Significance statement The addition of a methyl group to the N6-position of adenosine (m 6 A) is a highly abundant chemical modification of RNA. However, the functional role of m 6 A in insects and the key enzymes that regulate its levels remains poorly understood. In this study, we explored putative methylase genes and demethylase genes in hundreds insect genomes, and identified an m 6 A RNA demethylase, ALKBH4, in the whitefly, Bemisia tabaci . We demonstrate that ALKBH4 oxidatively reverses mRNA methylation in vivo and in vitro, in combination with other components of the m 6 A pathway, plays an important role in whitefly development. These findings provide new insight into m 6 A methylation system of insect.

Bradysia odoriphaga Yang et Zhang (Diptera: Sciaridae) poses a grave threat to China's vegetable industry, with particular severity in Allium tuberosum (Asparagales: Alliaceae) cultivation. The indiscriminate use of toxic insecticides to control B. odoriphaga has raised pressing concerns regarding safety risks for humans and livestock. This study systematically evaluated the thermal tolerance of A. tuberosum roots and B. odoriphaga larvae or pupae across a gradient of water temperatures. Based on these finding, a novel 'drip irrigation system utilizing warm water' (DIWW) was developed as an innovative pest management solution. Results showed A. tuberosum roots exhibited robust tolerance to water temperatures below 50 degrees C, sustaining no observable growth impairment. However, exposure to 60 degrees C for more than 20 s caused complete root mortality. For B. odoriphaga larvae, complete mortality required 30 min at 40 degrees C, 30 min at 42 degrees C, 5 min at 45 degrees C, 20 s at 48 degrees C, and 10 s at 50 degrees C. Pupae demonstrated higher thermal resistance, with complete mortality achieved in 10 min at 45 degrees C, 1 min at 48 degrees C, and 20 s at 50 degrees C. Leveraging these critical disparities in thermal tolerance, the DIWW system was engineered with a 1.0-1.4 mm pipe orifice and plastic film coverage. By maintaining water temperatures between 42-50 degrees C during application, the system effectively eradicated B. odoriphaga populations while significantly enhancing A. tuberosum yield. This eco-friendly technology not only addresses the challenges of chemical pesticides overuse but also provides a transferable framework for integrated pest management in diverse crop systems.

Insecticide resistance can impose fitness costs, but whether these costs are amplified under environmental stress remains poorly understood. Here, we investigated the temperature-dependent expression of imidacloprid resistance-associated fitness costs in the Mediterranean whitefly, Bemisia tabaci MED, using age-stage, two-sex life-table analysis. A susceptible strain and an imidacloprid-resistant strain with a shared genetic background were evaluated on cotton under six constant temperatures (15, 20, 25, 30, 35, and 40 °C). Development, survival, longevity, reproduction, and demographic parameters were compared between strains across thermal conditions. Both strains completed development only between 15 and 30 °C, whereas extreme temperatures restricted population establishment. The resistant strain exhibited stronger disadvantages than the susceptible strain under suboptimal temperatures, particularly at 15 °C, with prolonged immature development, delayed reproduction, reduced fecundity, and decreased population growth potential. To quantify the additional impact of thermal stress beyond baseline resistance costs, excess temperature-dependent fitness costs were calculated using the 25 °C resistant-to-susceptible performance ratio as the reference. The resistant strain showed negative excess-cost values for multiple developmental, reproductive, and demographic traits at 15 °C and, to a lesser extent, at 30 °C, indicating that temperature deviation from favorable conditions disproportionately reduced resistant-strain performance. These results demonstrate that reduced thermal adaptation represents an additional ecological component of imidacloprid resistance-associated fitness costs. Incorporating environmental stress into resistance-cost assessments may improve predictions of resistant population persistence under fluctuating field conditions.

Uridine diphosphate (UDP)-glycosyltransferases are essential phase-II detoxification enzymes that glycosylate lipophilic endogenous and xenobiotic compounds and they are thought to play a role in driving the evolution of insecticide resistance. To examine if the resistance to thiamethoxam and imidacloprid was associated with enhancement of UDP-glycosyltransferase in the whitefly, Bemisia tabaci, we first conducted UDP enzyme activity assays in resistant and sensitive strains in the absence and presence of UGT inhibitors. We found that the UGT enzyme content of resistant whitefly was significantly 5.02- to 10.69-fold higher than that of sensitive whitefly. Individual UGT inhibitors effectively inhibited UGT activity in resistant strains and their effect was synergistic when applied in combination. We then used bioinformatic, molecular, genetic and in silico approaches to determine if UGT352A3 encoded a key enzyme linked to neonicotinoid resistance. In resistant strains, UGT352A3 expression was elevated 1.8- to 6.6-fold compared to susceptible strains, which correlated with higher resistance ratios. RNAi-mediated knockdown of UGT352A3 in resistant whitefly strains significantly heightened their sensitivity to the insecticides, thiamethoxam and imidacloprid. Molecular docking analyses further confirmed a strong binding affinity between UGT352A3 and thiamethoxam and imidacloprid, which supported a role in their metabolism. These findings suggest that UGT352A3 is a critical factor in the development of resistance to thiamethoxam and imidacloprid in whitefly, underscoring its important potential as a new pest resistance management target.

The whitefly Bemisia tabaci (Hemiptera: Gennadius) is a notorious and highly polyphagous agricultural pest that is well known for its ability to transmit a wide range of serious plant pathogenic viruses. The field populations of B. tabaci in some areas have developed resistance to thiamethoxam. We found that high expression of CYP6EM1 can enhance the resistance of B. tabaci to dinotefuran. It is unclear whether CYP6EM1 is involved in the resistance of B. tabaci to the same neonicotinoid pesticide, thiamethoxam. The results of the present study demonstrated that the expression of CYP6EM1 could be induced within 9 h after the exposure of B. tabaci adults to thiamethoxam. Molecular docking analyses, with a binding energy of-6.13 cal/mol, revealed a strong binding affinity between thiamethoxam and the CYP6EM1 protein, implying that CYP6EM1 may be involved in thiamethoxam resistance. Compared with that in the susceptible strain, the mRNA expression level of the CYP6EM1 gene was significantly greater in thiamethoxam-resistant strains (R#1, 9.93-fold, P = 0.0008; R#2, 40.43-fold, P = 0.0013; R#3, 27.40-fold, P = 0.0002; R#4, 21.63-fold, P = 0.0003 and R#5, 28.65-fold, P = 0.0006). Loss and gain of function studies in vivo were performed via RNA interference and transgenic expression in Drosophila melanogaster, and the results confirmed the role of CYP6EM1 in conferring such resistance. An in vitro metabolism assay revealed that CYP6EM1 directly metabolized 15.60 % of thiamethoxam. This study provides solid evidence for the critical role of CYP6EM1 in the metabolism of thiamethoxam, which contributes to resistance. Our work provides a deeper understanding of the mechanism underlying neonicotinoid resistance and contributes valuable insights for the sustainable management of global pests such as whiteflies.

Trade- offs between evolutionary gain and loss are prevalent in nature, yet their genetic basis is not well resolved. The evolution of insect resistance to insecticide is often associated with strong fitness costs; however, how the fitness trade- offs operates remains poorly understood. Here, we show that the mitogen- activated protein kinase (MAPK) pathway and its upstream and downstream actors underlie the fitness trade- offs associated with insecticide resistance in the whitefly Bemisia tabaci . Specifically, we find a key cytochrome P450 gene CYP6CM1 , that confers neonicotinoids resistance to in B. tabaci , is regulated by the MAPKs p38 and ERK through their activation of the transcription factor cAMP- response element binding protein. However, phosphorylation of p38 and ERK also leads to the activation of the transcription repressor Cap "n" collar isoform C (CncC) that negatively regulates exuperantia (Ex), vasa (Va), and benign gonial cell neoplasm (Bg ), key genes involved in oogenesis, leading to abnormal ovary growth and a reduction in female fecundity. We further demonstrate that the transmembrane G protein- coupled receptor (GPCR) neuropeptide FF receptor 2 (NPFF2) triggers the p38 and ERK pathways via phosphorylation. Additionally, a positive feedback loop between p38 and NPFF2 leads to the continuous activation of the MAPK pathways, thereby constitutively promoting neonicotinoids resistance but with a significant reproductive cost. Collectively, these findings provide fundamental insights into the role of cis- trans regulatory networks incurred by GPCR-MAPK signaling pathways in evolutionary trade- offs and applied knowledge that can inform the development of strategies for the sustainable pest control.

Neonicotinoid insecticides, which target insect nicotinic acetylcholine receptors (nAChRs), have been widely and intensively used to control the whitefly, Bemisia tabaci, a highly damaging, globally distributed, crop pest. This has inevitably led to the emergence of populations with resistance to neonicotinoids. However, to date, there have been no reports of target-site resistance involving mutation of B. tabaci nAChR genes. Here we characterize the nAChR subunit gene family of B. tabaci and identify dual mutations (A58T&R79E) in one of these genes (BTβ1) that confer resistance to multiple neonicotinoids. Transgenic D. melanogaster, where the native nAChR Dβ1 was replaced with BTβ1A58T&R79E, were significantly more resistant to neonicotinoids than flies where Dβ1 were replaced with the wildtype BTβ1 sequence, demonstrating the causal role of the mutations in resistance. The two mutations identified in this study replace two amino acids that are highly conserved in >200 insect species. Three-dimensional modelling suggests a molecular mechanism for this resistance, whereby A58T forms a hydrogen bond with the R79E side chain, which positions its negatively-charged carboxylate group to electrostatically repulse a neonicotinoid at the orthosteric site. Together these findings describe the first case of target-site resistance to neonicotinoids in B. tabaci and provide insight into the molecular determinants of neonicotinoid binding and selectivity.

BACKGROUND:Elucidating fitness cost associated with field-evolved insect resistance to insecticide is of particular importance to current sustainable pest control. The global pest whitefly Bemisia tabaci has developed resistance to many members of neonicotinoids, but little is known about whitefly resistance to neonicotinoid nitenpyram and its associated fitness cost. Using insecticide bioassay and life-table approach, this study aims to investigate nitenpyram resistance status in field-collected whitefly populations, and to explore whether such resistance is accompanied by a fitness cost. RESULTS:The bioassay results revealed that 14 of 29 whitefly populations displayed moderate to extremely high resistance to nitenpyram, demonstrating a widespread field-evolved resistance to nitenpyram. This field-evolved resistance in the whitefly has increased gradually over the past 3 years from 2021 to 2023. Further life-table study showed that two resistant whitefly populations exhibited longer developmental time, shorter lifespans of adult, and lower fecundity compared with the most susceptible population. The relative fitness cost of the two resistant populations was calculated as 0.69 and 0.56 by using net productive rate R0, which suggests that nitenpyram resistance comes with fitness cost in the whitefly, especially on reproduction. CONCLUSION:Overall, these results represent field-evolved high resistance to nitenpyram in the whitefly. The existing fitness costs associated with nitenpyram resistance are helpful to propose a suitable strategy for sustainable control of whiteflies by rotation or mixture of insecticide with different modes of action. © 2024 Society of Chemical Industry.

BACKGROUND: Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) is a major agricultural insect pest that causes severe economic losses worldwide. Several insecticides have been applied to effectively control this key pest. However, owing to the indiscriminate use of chemical insecticides, B. tabaci has developed resistance against these chemical compounds over the past several years.RESULTS: From 2019 to 2021, 23 field samples of B. tabaci were collected across China. Twenty species were identified as the Mediterranean 'Q' type (MED) and three were identified as MED/ Middle East-Asia Minor 1 mixtures. Subsequently, resistance of the selected populations to different insecticides was evaluated. The results showed that 13 populations developed low levels of resistance to abamectin. An overall upward trend in B. tabaci resistance toward spirotetramat, cyantraniliprole and pyriproxyfen was observed. In addition, resistance to thiamethoxam remained low-to-moderate in the 23 field populations.CONCLUSION: These findings suggest that the overall resistance of the field-collected B. tabaci populations has shown an upward trend over the years in China. We believe our study can provide basic data to support integrated pest management and insecticide resistance management of field B. tabaci in China.(c) 2023 Society of Chemical Industry.

BACKGROUND: Understanding the trade-offs between insecticide resistance and the associated fitness is of particular importance to sustainable pest control. One of the most devastating pest worldwide, the whitefly Bemisia tabaci, has developed resistance to various insecticides, especially the neonicotinoid group. Although neonicotinoid resistance often is conferred by P450s-mediated metabolic resistance, the relationship between such resistance and the associated fitness phenotype remains largely elusive. By gene cloning, quantitative reverse transcription (qRT)-PCR, RNA interference (RNAi), transgenic Drosophila melanogaster, metabolism capacity in vitro and 'two sex-age stage' life table study, this study aims to explore the molecular role of a P450 gene CYP4CS5 in neonicotinoid resistance and to investigate whether such resistance mechanism carries fitness costs in the whitefly.RESULTS: Our bioassay tests showed that a total of 13 field-collected populations of B. tabaci MED biotype displayed low-to-moderate resistance to thiamethoxam and clothianidin. Compared to the laboratory susceptible strain, we then found that an important P450 CYP4CS5 was remarkably upregulated in the field resistant populations. Such overexpression of CYP4CS5 had a good match with the resistance level among the whitefly samples. Further exposure to the two neonicotinoids resulted in an increase in CYP4CS5 expression. These results implicate that overexpression of CYP4CS5 is closely correlated with thiamethoxam and clothianidin resistance. RNAi knockdown of CYP4CS5 increased mortality of the resistant and susceptible populations after treatment with thiamethoxam and clothianidin in bioassay, but obtained an opposite result when using a transgenic line of D. melanogaster expressing CYP4CS5. Metabolic assays in vitro revealed that CYP4CS5 exhibited certain capacity of metabolizing thiamethoxam and clothianidin. These in vivo and in vitro assays indicate an essential role of CYP4CS5 in conferring thiamethoxam and clothianidin resistance in whitefly. Additionally, our life-table analysis demonstrate that the field resistant whitefly exhibited a prolonged development time, shortened longevity and reduced fecundity compared to the susceptible, suggesting an existing fitness cost as a result of the resistance.CONCLUSION: Collectively, in addition to the important role of CYP4CS5 in conferring thiamethoxam and clothianidin resistance, this resistance mechanism is associated with fitness costs in the whitefly. These findings not only contribute to the development of neonicotinoids resistance management strategies, but also provide a new target for sustainable whitefly control. (c) 2023 Society of Chemical Industry.

Being a destructive pest worldwide, the whitefly Bemisia tabaci has evolved resistance to neonicotinoid insecticides. The third-generation neonicotinoid dinotefuran has commonly been applied to the control of the whitefly, but its underlying mechanism is currently unknown. On the base of our transcriptome data, here we aim to investigate whether the cytochrome P450 CYP6EM1 underlies dinotefuran resistance in the whitefly. Compared to the susceptible strain, the CYP6EM1 gene was found to be highly expressed in both laboratory and field dinotefuran-resistant populations. Upon exposure to dinotefuran, the mRNA levels of CYP6EM1 were increased. These results demonstrate the involvement of this gene in dinotefuran resistance. Loss and gain of functional studies in vivo were conducted through RNAi and transgenic Drosophila melanogaster assays, confirming the role of CYP6EM1 in conferring such resistance. In a metabolism assay in vitro, the CYP6EM1 protein could metabolize 28.11% of dinotefuran with a possible dinotefuran-dm-NNO metabolite via UPLC-QTOF/MS. Docking of dinotefuran to the CYP6EM1 protein showed a good binding affinity, with an energy of less than -6.0 kcal/mol. Overall, these results provide compelling evidence that CYP6EM1 plays a crucial role in the metabolic resistance of B. tabaci to dinotefuran. Our work provides new insights into the mechanism underlying neonicotinoid resistance and applied knowledge that can contribute to sustainable control of a global pest such as whitefly.

Bemisia tabaci (Hemiptera: Gennadius) is a notorious pest that is capable of feeding on >600 kinds of agricultural crops. Imidacloprid is critical in managing pest with sucking mouthparts, such as B. tabaci. However, the field population of B. tabaci has evolved resistance because of insecticide overuse. The overexpression of the detoxification enzyme cytochrome P450 monooxygenase is considered the main mechanism of imidacloprid resistance, but the mechanism underlying gene regulation remains unclear. MicroRNAs are a type of endogenous small molecule compounds that is fundamental in regulating gene expression at the post-transcriptional level. Whether miRNAs are related to the imidacloprid resistance of B. tabaci remains unknown. To gain deep insight into imidacloprid resistance, we conducted on miRNAs expression profiling of two B. tabaci Mediterranean (MED) strains with 19-fold resistance through deep sequencing of small RNAs. A total of 8 known and 1591 novel miRNAs were identified. In addition, 16 miRNAs showed significant difference in expression levels between the two strains, as verified by quantitative reverse transcription PCR. Among these, novel_miR-376, 1517, and 1136 significantly expressed at low levels in resistant samples, decreasing by 36.9%, 60.2%, and 15.6%, respectively. Moreover, modulating novel_miR-1517 expression by feeding with 1517 inhibitor and 1517 mimic significantly affected B. tabaci imidacloprid susceptibility by regulating CYP6CM1 expression. In this article, miRNAs related to imidacloprid resistance of B. tabaci were systematically screened and identified, providing important information for the miRNA-based technological innovation for this pest management.

Bemisia tabaci has developed high resistance to many insecticides and causes substantial agricultural and economic losses annually. The insecticide resistance of whitefly has been widely reported in previous studies; however, the underlying mechanism remains little known. In this study, we cloned two P450 genes: CYP6DW3 and CYP6DW5v1; these genes were markedly overexpressed in imidacloprid-resistant whitefly populations compared with susceptible populations, and knockdown of these genes decreased the imidacloprid resistance of whitefly. Moreover, heterologous expression of whitefly P450 genes in SF9 cells and metabolic studies showed that the CYP6DW3 protein could metabolize 14.11% imidacloprid and produced imidacloprid-urea in vitro. Collectively, the expression levels of CYP6DW3 and CYP6DW5v1 are positively correlated with imidacloprid resistance in B. tabaci. Our study further reveals that cytochrome P450 enzymes affect the physiological activities related to resistance in insects, which helps scholars more deeply understand the resistance mechanism, and contributes to the development of integrated pest management framework.

The whitefly, Bemisia tabaci, comes up high metabolic resistance to most neonicotinoids in long-term evolution, which is the key problem of pest control. UGT glycosyltransferase, as a secondary detoxification enzyme, plays an indispensable role in detoxification metabolism. In this study, UGT inhibitors, 5-nitrouracil and sulfinpyrazone, dramatically augmented the toxic damage of neonicotinoids to B. tabaci. A UGT named UGT353G2 was identified in whitefly, which was notably up-regulated in resistant strain (3.92 folds), and could be induced by most neonicotinoids. Additionally, the using of RNA interference (RNAi) suppresses UGT353G2 substantially increased sensitivity to neonicotinoids in resistant strain. Our results support that UGT353G2 may be involved in the neonicotinoids resistance of whitefly. These findings will help further verify the functional role of UGTs in neonicotinoid resistance.

The sweet potato whitefly, Bemisia tabaci, (Gennadius) (Hemiptera:Aleyrodidae) is a global pest of crops. Neonicotinoids are efficient insecticides used for control of this pest. Insecticidal targets of neonicotinoids are insect nicotinic acetylcholine receptors (nAChRs). Here, we characterized and cloned the full length of the nAChR β1 subunit (BTβ1) in B. tabaci and confirmed the consistency of BTβ1 in B. tabaci MEAM1 and MED. Expression levels of BTβ1 in different developmental stages and body parts of adults were investigated and compared in B. tabaci MED. dsRNA was prepared to knock down BTβ1 in adult B. tabaci and significantly decreases the susceptibility to five neonicotinoid insecticides, including imidacloprid, clothianidin, thiacloprid, nitenpyram, and dinotefuran. This study indicated BTβ1 as a notable site influencing the susceptibility of B. tabaci to neonicotinoids.

Cuticular proteins (CPs) play an important role in protecting insects from adverse environmental conditions, like neonicotinoid insecticides, which are heavily used for numerous pests and caused environmental problems and public health concerns worldwide. However, the relationship between CPs and insecticides resistance in Bemisia tabaci, a serious and developed high insecticide resistance, is lacking. In this study, 125 CPs genes were identified in B. tabaci. Further phylogenetic tree showed the RR-2-type genes formed large gene groups in B. tabaci. Transcriptional expression levels of CPs genes at different developmental stages revealed that some CPs genes may play a specific role in insect development. The TEM results indicated that the cuticle thickness of susceptible strain was thinner than imidacloprid-resistance strain. Furthermore, 16 CPs genes (5 in RR-1 subfamily, 7 in RR-2 subfamily, 3 in CPAP3 subfamily and 1 in CPCFC subfamily) were activated in response to imidacloprid. And RNAi results indicated that CP9 and CP83 involved in imidacloprid resistance. In conclusion, this study was the first time to establish a basic information framework and evolutionary relationship between CPs and imidacloprid resistance in B. tabaci, which provides a basis for proposing integrated pest management strategies.

BackgroundDifference in physiology level between the immature and mature stages of insects likely contribute to different mechanisms of insecticide resistance. It is well acknowledged that insect 20-hydroxyecdysone (20E) plays an important role in many biological processes in the immature stage, whether 20E confers insecticide resistance at this specific stage is still poorly understood. By gene cloning, reverse transcription quantitative real-time PCR, RNA interference (RNAi) and in vitro metabolism experiments, this study aimed to investigate the potential role of 20E-related genes in conferring imidacloprid (IMD) resistance in the immature stage of the whitefly Bemisia tabaci Mediterranean. ResultsAfter identification of low to moderate IMD resistance in the whitefly, we found CYP306A1 of the six 20E-related genes was overexpressed in the nymph stage of the three resistant strains compared to a laboratory reference susceptible strain, but not in the adult stage. Further exposure to IMD resulted in an increase in CYP306A1 expression in the nymph stage. These results together imply that CYP306A1 may be implicated in IMD resistance in the nymph stage of the whitefly. RNAi knockdown of CYP306A1 increased the mortality of nymphs after treatment with IMD in bioassay, suggesting a pivotal role of CYP306A1 in conferring IMD resistance in the nymph stage. Additionally, our metabolism experiments in vivo showed that the content of IMD reduced by 20% along with cytochrome P450 reductase and heterologously expressed CYP306A1, which provides additional evidence for the important function of CYP306A1 in metabolizing IMD that leads to the resistance. ConclusionThis study uncovers a novel function of the 20E biosynthesis gene CYP306A1 in metabolizing imidacloprid, thus contributing to such resistance in the immature stage of the insect. These findings not only advance our understanding of 20E-mediated insecticide resistance, but also provide a new target for sustainable pest control of global insect pests such as whitefly. (c) 2023 Society of Chemical Industry.

Cytochrome P450 monooxygenases (P450s) are well-known for their crucial roles in the detoxification of xenobiotics. However, whether CYP6CX2 and CYP6CX3, 2 genes from our Bemisia tabaci (B. tabaci) MED/Q genome data were associated with detoxification metabolism and confer resistance to thiamethoxam is unclear. In this study, we investigated the role of CYP6CX2 and CYP6CX3 in mediating whitefly thiamethoxam resistance. Our results showed that mRNA levels of CYP6CX2 and CYP6CX3 were up-regulated after exposure to thiamethoxam. Transcriptional levels of 2 genes were overexpressed in laboratory and field thiamethoxam resistant strains by RT-qPCR. These results indicate that the enhanced expression of CYP6CX2 and CYP6CX3 appears to confer thiamethoxam resistance in B. tabaci. Moreover, linear regression analysis showed that the expression levels of CYP6CX2 and CYP6CX3 were positively correlated with thiamethoxam resistance levels among populations. The susceptibility of whitefly adults was markedly increased after silencing 2 genes by RNA interference (RNAi) which further confirming their major role in thiamethoxam resistance. Our findings provide information to better understand the roles of P450s in resistance to neonicotinoids and suggest that these genes may be applied to develop target genes for sustainable management tactic of agricultural pests such as B. tabaci.

High level resistance for a variety of insecticides has emerged in Bemisia tabaci, a globally notorious insect. Neonicotinoid insecticides have been applied widely to control B. tabaci. Whether a differentially expressed gene CYP6DB3 discovered from transcriptome data of B. tabaci is involved in the resistance to neonicotinoid insecticides remains unclear. In the study, CYP6DB3 expression was significantly up-regulated in both thiamethoxam- and imidacloprid-resistant strains relative to the susceptive strains. We also found that CYP6DB3 expression was up-regulated after B. tabaci adults were exposed to thiamethoxam and imidacloprid. Moreover, knocking down CYP6DB3 expression via feeding corresponding dsRNA significantly reduced CYP6DB3 mRNA levels by 34.1%. Silencing CYP6DB3 expression increased the sensitivity of B. tabaci Q adults against both thiamethoxam and imidacloprid. Overexpression of CYP6DB3 gene reduced the toxicity of imidacloprid and thiamethoxam to transgenic D. melanogaster. In addition, metabolic studies showed that CYP6DB3 can metabolize 24.41% imidacloprid in vitro. Collectively, these results strongly support that CYP6DB3 plays an important role in the resistance of B. tabaci Q to imidacloprid and thiamethoxam. This work will facilitate a deeper insight into the part of cytochrome P450s in the evolution of insecticide resistance and provide a theoretical basis for the development of new integrated pest resistance management.

为了有效防控柑橘大实蝇,本文利用触角电位仪和"Y"形嗅觉仪测定初羽化的柑橘大实蝇成虫对4种不同浓度(0.5、1.0、5.0、10.0μg/μL)的14种板栗挥发物的触角电位(EAG)反应和嗅觉行为反应差异.结果表明,柠檬烯、α-蒎烯、苯乙酸甲酯、异丁醛、芳樟醇、β-石竹烯和苯乙醛对初羽化柑橘大实蝇成虫具有显著或极显著的引诱作用,戊醛、乙偶姻、乙酸芳樟酯和水杨酸甲酯对柑橘大实蝇成虫表现出显著或极显著的驱避作用,壬醛对柑橘大实蝇雌虫具有极显著的驱避作用、对柑橘大实蝇雄虫具有极显著的引诱作用.初羽化的柑橘大实蝇成虫对14种板栗挥发物之间的EAG反应存在极显著差异,对柠檬烯的EAG反应相对值最高(2.060±0.071),对戊醛的EAG反应相对值最低(0.455±0.050),其最高EAG反应相对值是最低的4.52倍;其余12种挥发物的EAG反应相对值介于二者之间.