Expression profile of CYP402C1 and its role in resistance to imidacloprid in the whitefly, Bemisia tabaci

Molecular identification of three cytochrome P450 genes and their potential roles in insecticides tolerance in Grapholita molesta (Busck)

The oriental fruit moth, Grapholita molesta (Busck), is a significant pest of Rosaceae trees worldwide and has developed resistance to various insecticides. Cytochrome P450 play a major role in detoxification of resistance to insecticides in insects. In this study, we found that Piperonyl butoxide (PBO), which inhibits the P450 activity, synergized with abamectin, imidacloprid, and L-cyhalothrin, increasing mortality rates of G. molesta by 43.04 %, 31.66 %, and 59.09 %, respectively. Using previously constructed transcriptome data from G. molesta treated with these three insecticides, we identified and cloned three new cytochrome P450 genes-CYP4L57 (OR027029), CYP9A114 (OR027031), and CYP9A203 (OR027030). These genes were highly expressed in adults, with CYP4L57 showing a 123.90-fold increase, CYP9A114 a 43.89-fold increase, and CYP9A203 a 1498.99-fold increase compared to egg stages. Tissue-specific expression analysis revealed CYP4L57 was predominantly expressed in the head, CYP9A114 in the hindgut, fat body, and Malpighian tubules, and CYP9A203 in the midgut, ovary, and hindgut. Molecular docking demonstrated strong binding interactions between these P450 genes and the insecticides. RNA interference-mediated silencing of CYP4L57, CYP9A114, and CYP9A203 significantly increased mortality rates by 12.42 % to 68.89 % upon exposure to the insecticides, abamectin, imidacloprid, and L-cyhalothrin. These findings suggest that cytochrome P450 genes contribute to insecticide tolerance in G. molesta and CYP4L57, CYP9A114, and CYP9A203 play key roles in this process.

Role of CYP311A1 in wing development of Drosophila melanogaster

Lipid homeostasis is crucial for growth and development of organisms. Several cytochrome P450 monooxygenases (CYPs) are involved in lipid metabolism. The function of Cyp311a1 in the anterior midgut as a regulator of phosphatidylethanolamine (PE) metabolism in Drosophila melanogaster has been demonstrated, as depletion of Cyp311a1 caused larval growth arrest that was partially rescued by supplying PE. In this study, we investigated the role of CYP311A1 in wing morphogenesis in Drosophila. Using the GAL4-UAS system, Cyp311a1 was selectively knocked down in the wing disc. A deformed wing phenotype was observed in flies with reduced Cyp311a1 transcripts. BODIPY and oil red O staining revealed a reduction of neutral lipids in the wing disc after the depletion of Cyp311a1. In addition, we observed an enhanced sensitivity to Eosin Y penetration in the wings of Cyp311a1 knocked-down flies. Moreover, the reduction of CYP311A1 function in developing wings does not affect cell proliferation and apoptosis, but entails disordered Phalloidin or Cadherin distribution, suggesting an abnormal cell morphology and cell cortex structure in wing epithelial cells. Taken together, our results suggest that Cyp311a1 is needed for wing morphogenesis by participating in lipid assembly and cell homeostasis.

Overexpression of CYP6CX4 contributing to field-evolved resistance to flupyradifurone, one novel butenolide insecticide, in Bemisia tabaci from China

Bemisia tabaci is a formidable insect pest worldwide, and exhibits significant resistance to various insecticides. Flupyradifurone is one novel butenolide insecticide and has emerged as a new weapon against B. tabaci, but field-evolved resistance to this insecticide has become a widespread concern. To unravel the mechanisms of field-evolved flupyradifurone resistance, we conducted a comprehensive investigation into susceptibility of twenty-one field populations within the Beijing-Tianjin-Hebei Region of China. Alarmingly, thirteen of these populations displayed varying degrees of resistance, ranging from low to medium levels, and building upon our prior findings, we meticulously cloned and characterized the CYP6CX4 gene in B. tabaci. Our investigations unequivocally confirmed the association between CYP6CX4 overexpression and flupyradifurone resistance in three of the thirteen resistant strains via RNA interference. To further validate our findings, we introduced CYP6CX4 overexpression into a transgenic Drosophila melanogaster line, resulting in a significant development of resistance to flupyradifurone in D. melanogaster. Additionally, homology modeling and molecular docking analyses showed the stable binding of flupyradifurone to CYP6CX4, with binding free energy of -6.72 kcal mol-1. Collectively, our findings indicate that the induction of CYP6CX4 exerts one important role in detoxification of flupyradifurone, thereby promoting development of resistance in B. tabaci.

Enhancement of tolerance against flonicamid in Solenopsis invicta (Hymenoptera: Formicidae) through overexpression of CYP6A14

Solenopsis invicta is a main issue in southern China and is causing significant damage to the local ecological environment. The extensive use of insecticides has resulted in the development of tolerance in S. invicta. In our study, ten S. invicta colonies from Sichuan Province exhibited varying degrees of tolerance against flonicamid, with LC50 values from 0.49 mg/L to 8.54 mg/L. The sensitivity of S. invicta to flonicamid significantly increased after treatment with the P450 enzyme inhibitor piperonyl butoxide (PBO). Additionally, the activity of P450 in S. invicta was significantly enhanced after being treated with flonicamid. Flonicamid induced the expression levels of CYP4aa1, CYP9e2, CYP4C1, and CYP6A14. The expression levels of these P450 genes were significantly higher in the tolerant colonies compared to the sensitive colonies, and the relative copy numbers of CYP6A14 in the tolerant colonies were 2.01-2.15 fold. RNAi feeding treatment effectively inhibited the expression of P450 genes, thereby reducing the tolerance of S. invicta against flonicamid. In addition, the overexpression of CYP6A14 in D. melanogaster resulted in reduced sensitivity to flonicamid. Our investigations revealed hydrophobic interactions between flonicamid and seven amino acid residues of CYP6A14, along with the formation of a hydrogen bond between Glu306 and flonicamid. Our findings suggest that flonicamid can effectively control S. invicta and P450 plays a pivotal role in the tolerance of S. invicta against flonicamid. The overexpression of CYP6A14 also increased tolerance to flonicamid.

20E biosynthesis gene CYP306A1 confers resistance to imidacloprid in the nymph stage of Bemisia tabaci by detoxification metabolism

BACKGROUND

Difference 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.

RESULTS

After 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.

CONCLUSION

This 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. © 2023 Society of Chemical Industry.

CYP6DW3 Metabolizes Imidacloprid to Imidacloprid-urea in Whitefly (Bemisia tabaci)

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.

Resistance to dinotefuran in Bemisia tabaci in China: status and characteristics

BACKGROUND

Bemisia tabaci (Gennadius) is a serious agricultural pest worldwide. Neonicotinoids are the most important new class of synthetic insecticides used in the management of B. tabaci. However, B. tabaci populations have developed resistance to various active ingredients in neonicotinoids following long-term and widespread application.

RESULTS

Dinotefuran exhibited high toxicity against most B. tabaci field populations. One population (Din-R) with a high level of resistance to dinotefuran (255.6-fold) was first identified in the field. The Din-R population exhibited medium to high levels of resistance to all the tested neonicotinoid insecticides and a high level of resistance to spinetoram. Genetic inheritance analysis revealed that resistance to dinotefuran was incompletely recessive and polygenic. The synergist piperonyl butoxide significantly increased the toxicity of dinotefuran to Din-R. P450 activity in the Din-R population was 2.19-fold higher than in the susceptible population. RNA-sequencing analysis showed that 12 P450 genes were significantly upregulated in the Din-R population, of which CYP6DW5, CYP6JM1 and CYP306A1 were found to exhibit more than 3.00-fold higher expression in Din-R when using a reverse transcription quantitative real-time polymerase chain reaction. Expression of eight P450 genes was obviously induced by dinotefuran, and CYP6DW5 showed the highest expression level. After knockdown of CYP6DW5 in Din-R, the toxicity of dinotefuran increased significantly.

CONCLUSION

P450 had a crucial role in dinotefuran resistance in B. tabaci, and CYP6DW5 was involved in the resistance. These results provide important information for the management of resistance in B. tabaci and improve our understanding of the resistance mechanism of dinotefuran. © 2022 Society of Chemical Industry.

Cytochrome P450 Gene, CYP6CX3, Is Involved in the Resistance to Cyantraniliprole in Bemisia tabaci

Bemisia tabaci is an important agricultural sucking pest, and it develops serious resistance to various insecticides. Although cytochrome P450 was involved in the resistance to cyantraniliprole, limited studies have been conducted on B. tabaci. In the present study, piperonyl butoxide significantly increased the toxicity of cyantraniliprole. P450 activities in two resistant populations were 1.97- and 2.17-fold higher than that in the susceptible population. Among 79 P450 genes, CYP6CX3 expressions in two resistant populations were 3.08- and 3.67-fold higher than that in the susceptible population. When CYP6CX3 was knocked down, the toxicity of cyantraniliprole increased significantly. The LC₅₀ value of cyantraniliprole to the Drosophila melanogaster line overexpressing B. tabaci CYP6CX3 increased 7.34-fold. The content of cyantraniliprole was decreased by 25.74 ± 4.27% after mixing with CYP6CX3 and CPR for 2 h. These results suggested that the overexpression of CYP6CX3 was likely involved in the resistance to cyantraniliprole in B. tabaci.