Sclerotinia stem rot caused by Sclerotinia sclerotiorum is one of the most serious diseases of oilseed rape. Chemical control is an important method to control this disease, however, development of fungal resistance to commonly used fungicides has led to severe yield losses in recent years. Therefore, development of novel fungicides against S. sclerotiorum is urgently needed. Glabridin is one of the major flavonoids in Glycyrrhiza L. plants, and we previously found that it is very effective against S. sclerotiorum. Nevertheless, the baseline sensitivity and resistance risk of S. sclerotiorum to glabridin as well as the possible anti-fungal mechanism need further elucidation. In this study, we revealed that the EC (median effective concentration) values of glabridin against 109 S. sclerotiorum isolates collected from Jiangsu Province of China ranged from 0.51 to 8.03 μg/mL with a mean EC value of 3.05 ± 1.27 μg/mL. No cross-resistance was observed between glabridin and carbendazim, and no glabridin-resistant mutants were obtained by chemical induction. RNA profiling result showed that tyrosine metabolism of S. sclerotiorum were evidently affected by glabridin. qRT-PCR, enzyme activity assay, and molecular docking proved that glabridin greatly reduced both the expression level and enzyme activity of tyrosinase in S. sclerotiorum. Furthermore, S. sclerotiorum incurred certain impairment in its membrane integrity after glabridin treatment at 10 μg/mL. This study is the first report on baseline sensitivity and resistance risk of S. sclerotiorum to glabridin, and it is revealed that glabridin may interfere tyrosine metabolism and membrane integrity of S. sclerotiorum.

Acting as an extremely promising fungal pesticide, Metarhizium rileyi exhibits robust insecticidal activity against Lepidoptera pests, particularly the larvae. Though there is a slight delay in efficacy, biopesticides offer salient advantages over traditional chemical pesticide especially in environmental safety, cyclic infection and resistant inhibition. In this study, an exterior T-DNA was randomly inserted into the genome of M. rileyi, resulting in the acquisition of a mutant strain that displayed a colour transition from green to yellow within its conidia. The disruption of Mrlac1, a laccase, has been confirmed to attribute to the epigenetic alterations. Mrlac1 is a secreted protein harboring an N-terminal signaling peptide that undergoes in vivo synthesis and accumulates on the cell wall of M. rileyi. Targeted knock-out mutant exhibited alterations not just in conidia coloration, but significantly diminished capacity to withstand external stressors, particularly non-biological factors such as high humidity, Congo red exposure, and UV radiation. The disruptant suffered a constraint on hyphal polar growth, alteration in conidial surface structure, as well as noticeable increase in adhesion forces between conidia, the core infection factors. There is a remarkable diminution in virulence of Mrlac1 deletion variant against larvae of Spodoptera litura by topical inoculation, but not hemolymph injection. Our findings suggest that Mrlac1 acts as a positive regulator in the normal morphogenesis of fungal conidia, encompassing pigment production, inter-conidia adhesion, and conidial cell wall integrity, while the preservation of these structures holds paramount importance for the survival and infection of M. rileyi in the field.

It is urgent to solve insecticide resistance issues for fall armyworm (FAW), Spodoptera frugiperda. Some acetylcholinesterase-1 (Ace-1) mutations (A201S, G227A and F290V) have been identified as a cause of FAW resistance to organophosphates (OPs) and carbamates insecticides (CXs). However, the structural biological mechanisms on the relationship between the Ace-1 mutations and resistance to OPs and CXs still remain elusive. In this study, the A201S and F290V mutaions were found in eight fields populations of FAW except the G227A. Molecular docking revealed that the four Ace-1 proteins (Ace1-WT, Ace1-A201S, Ace1-G227A and Ace1-F290V) had the same binding modes and the same binding energies with acetylcholine (Ach), trichlorfon, chlorpyrifos, methomyl, carbaryl and chlorpyrifos oxide. The structural biological analysis revealed that the A201S mutations can enhance enzyme catalytic efficiency by introducing the hydroxyl group (-OH) from serine which performed the same function as the main-chain -NH and enhanced the interaction with the carboxy oxygen of acetylcholine (Ach), and the F290V mutation can effectively improve FAW resistance to insecticides by increasing the likelihood of Ach to enter the enzyme's active center for phenylalanine replaced by smaller valine under insecticide inhibition conditions. The bioassays and age-stage-specific life table analysis of FAW-SS and FAW-F290V populations revealed that F290V mutation effectively contributed to FAW resistance with a low fitness cost. This study provides a theoretical basis for future pest resistance management.

Ecdysone receptor (EcR) and three insect chitinases (OfChtI, OfChtII, and OfChi-h) are considered as attractive targets for the development of novel insect growth regulators (IGRs) since they are closely related to the insect molting. In this study, to develop potent multi-target IGRs, a series of hexacyclic pyrazol-3-amide derivatives were rationally designed by utilizing the scaffold hopping strategy with the previously reported compound 6j (N-(4-bromobenzyl)-2-phenyl-4,5,6,7-tetrahydro-2H-indazole-5-carboxamide) as a lead compound. The bioassay results indicated that most of the target compounds exhibited obvious insecticidal activity. Especially, compounds a5 and a21 displayed excellent insecticidal activities against P. xylostella with LC values of 82.29 and 69.45 mg/L, respectively, exceeding that of 6j (263.78 mg/L). Compounds a5 and a21 also dramatically disturbed the growth and development of O. furnacalis larvae, and their LC values were 124.71 and 127.54 mg/L, respectively, superior to the lead 6j (267.33 mg/L). The action mechanism study revealed that the most active compound a21 could act simultaneously on EcR (21.4 % binding activity at 8 mg/L), OfChtI (94.9 % inhibitory at 10 μM), OfChtII (23.1 % inhibitory at 10 μM), and OfChi-h (94.3 % inhibitory at 10 μM), significantly higher than that of the lead compound 6j. The result of molecular docking indicated that transferring the carboxamide group from pyrazole position 5 to 3 enhanced the interactions of a21 with the key amino acid residues of the OfChtI, OfChtII, and OfChi-h, resulting in stronger affinity to the three targets than 6j. The present work offers a useful guidance for the further development of novel multi-target IGRs.

The greater wax moth Galleria mellonella is a cosmopolitan pest of hives of the western honey bee Apis mellifera, where it remains exposed to varroicides applied by beekeepers in past decades as pest management chemicals for control of Varroa destructor, a devastating ectoparasite of bees. The prolonged presence of coumaphos residues, an organophosphate varroicide, in beeswax may be responsible for current levels of tolerance exhibited by G. mellonella, a non-target species that infests beehives. In this study, a field-collected strain of waxworms exhibited a higher LC value for coumaphos than that of a laboratory strain that had not been continuously exposed to coumaphos residues at field concentrations. Despite its higher tolerance for coumaphos, the field strain experienced growth inhibition at ecologically relevant concentration of coumaphos. Moreover, at low environmental concentrations that did not alter growth, detoxification gene expression levels were substantially altered. RNA-Seq analysis revealed 1181 and 658 differentially expressed genes in fat body and midgut, respectively, with 378 and 186 of those genes upregulated. This large-scale upregulation encompassed 21 genes encoding cytochrome P450 monooxygenases (CYPs), 13 encoding UDP-glycosyltransferases (UGTs), 5 encoding glutathione-S-transferases (GSTs), 2 encoding carboxylesterases (COEs), and 2 encoding ABC transporters (ABCs) in either tissue. Expression analysis of 13 selected candidate detoxification genes by RT-qPCR was consistent with their expression from RNA-Seq data. In sum, our results indicate that long-lasting pesticide residues in beeswax from past Varroa mite management may continue to act as selective agents on detoxification systems of hive residents other than the initial target species and that multiple resistance mechanisms to these chemicals may coexist within the beehive fauna.

Resmethrin, a pyrethroid pesticide used to control insects, is toxic to non-target organisms and other mammals. However, little is known about the reproductive toxicity of resmethrin in the testes, or its mechanism of toxicity. In this study, we investigated the testicular toxicity of resmethrin on mouse Leydig (TM3) and Sertoli (TM4) cells, focusing on the mitochondria and endoplasmic reticulum (ER). We found that resmethrin inhibited proliferation and cell cycle progression and disrupted mitochondrial membrane potential (MMP; ΔΨ) in TM3 and TM4 cells. In particular, resmethrin exposure significantly reduced the expression of mitochondria-associated membranes (MAMs) proteins, such as Vapb, Vdac, and Grp75, in both cell lines. Resmethrin also disrupts calcium homeostasis in the mitochondrial matrix and cytoplasm. In addition, resmethrin activates oxidative stress-mediated ER stress signals. Finally, we confirmed that 4-PBA, an ER stress inhibitor, restored the growth of TM3 and TM4 cells, which was decreased by resmethrin. Therefore, we confirmed that resmethrin hampered MAMs and activated ER stress, thus suppressing TM3 and TM4 cell proliferation.

The Janus kinase/signal transducer and activator of transcription (JAK/STAT) signaling pathway within the innate immune system plays a crucial role in defending insects against bacterial, fungal, and viral pathogens. In this study, we identified and cloned five key genes of this signaling pathway in Myzus persicae: MpDome-1, MpDome-2, MpJak, MpStat92E-1, and MpStat92E-2. Our results illustrated that these genes were highly expressed in first, second and third-instar nymphs. Tissue-specific expression analysis revealed that the five genes were predominantly expressed in the gut. Upon bacterial challenge, particularly with Staphylococcus aureus, the expression levels of all five genes were significantly upregulated. Additionally, Escherichia coli infection significantly upregulated the expression levels of MpDome-1 and MpDome-2, while MpJak, MpStat92E-1 and MpStat92E-2 were weakly upregulated. Functional analysis through RNA interference-mediated knockdown of these target genes revealed a significant increase in mortality following infection with E. coli and S. aureus compared with the control group. These findings suggest that the JAK/STAT signaling pathway is crucial for immune defense against bacterial infections in M. persicae.

Monocrotaline (MCT) is a toxic alkaloid present in plants, posing a threat to animals in terrestrial ecosystems. However, little is known about its potential impacts on pollinating insects. Here, we report the effects of of MCT on the brains and intestines of foraging honeybees (Apis mellifera). MCT exposure resulted in a reduction in head weight and swelling of the abdomen in honeybees. Additionally, MCT exposure caused morphological damage to the brain, characterized by decreased antioxidant capacity and increased apoptosis, along with intestinal tissue damage that was accompanied by increased antioxidant capacity and apoptosis. Moreover, MCT altered the core gut microbial community structure in honeybees and increased the expression of antimicrobial peptide (AMP) genes in the midgut. These findings indicate that exposure to MCT activates the immune response in the honeybee gut, while the brain does not exhibit an immune response but instead experiences oxidative stress. This study provides a resource for future research exploring interactions between MCT and other insects, and can help deepen our understanding of MCT's potential impacts in ecosystems.

Glutathione S-transferases (GSTs) are an important class of enzymes that facilitate the conjugation of reduced glutathione (GSH) with electrophilic substrates, including some insecticides. Two inhibitors of GSTs, ethacrynic acid (EA) and diethyl maleate (DEM), are often used as diagnostic tools to implicate GST involvement in insecticide resistance, but their modes of action against insect GSTs are largely assumed based on mammalian studies. In mammalian studies, there are two proposed mechanisms of inhibition of GST function by EA and DEM: 1) scavenging or "depleting" cytosolic GSH through non-enzymatic conjugation, and 2) inhibition of GST activity directly by the inhibitor-GSH conjugate (EA-SG and DEM-SG). The objective of this study was to characterize putative inhibitory mechanisms of EA and DEM against insect (house fly) GSTs and the co-factor GSH. Both EA and DEM synergized topical applications of naled and propoxur but not permethrin. As a GSH scavenger, EA was ∼10-fold more potent compared to DEM. Conditions such as pH, GSH concentration, and incubation time significantly affected the ability of both inhibitors to scavenge GSH. EA demonstrated scavenging at a wider pH range than DEM and scavenged GSH at a faster rate than DEM. Whereas EA peak scavenging was observed almost instantly, there was a 54.4 % increase in scavenged GSH for DEM between 0 and 30 min of incubation. Increasing concentration of GSH diminished the effect of scavenging at the highest tested concentrations of both inhibitors. In the presence of both GSH and GSTs in crude homogenate, EA was 300-fold more potent as a GST inhibitor compared to DEM at pH 7.5. No comparison was made at pH 6.5 because the tested concentrations of DEM did not produce enough inhibition to derive an IC value while EA concentrations did. With purified GSTs, EA-SG was 205-fold more potent as an inhibitor compared to DEM-SG, while EA alone was 7.6-fold more potent than EA-SG and 1565-fold more potent than DEM-SG. These findings establish in insects that the insecticide synergists EA and DEM function mainly by scavenging the GST co-factor GSH, with some inhibition due to interactions with GSTs and the inhibitor-GSH conjugates, rather than through interaction between the inhibitors and the GST protein itself. These resulting impacts are two-fold, whereby (i) GSH bioavailability is limited and (ii) the GSH-inhibitor complex attenuates GST-based xenobiotic metabolism.

Rapamycin is a lipophilic macrolide antibiotic which is famous for its immunosuppressive and anticancer activity. In recent years, rapamycin showed significant activity against various plant pathogenic fungi. However, the sensitivity of Colletotrichunm fungi to rapamycin is scarcely reported. In this study, we evaluated the sensitivity of 116 Colletotrichum isolates from tea-oil trees to rapamycin. Most isolates exhibited natural resistance with inhibition rates of 50 to 70% at 50 μg/mL. Three Colletotrichum camelliae isolates were found to be sensitive to rapamycin. No mutations were detected in the direct target FKBP12 and indirect target TOR-FRB domain of resistant and sensitive C. camelliae isolates. Notably, the expression of the TOR homolog (CcTOR) was higher in resistant C. camelliae isolates compared to the sensitive ones and overexpression of CcTOR in the sensitive isolate CcS1 resulted in decreased sensitivity to rapamycin. Moreover, ribosomal protein S6 phosphorylation was abolished in the sensitive isolate CcS1 but not in the resistant isolate CcR1 under rapamycin treatment. In addition, the expression levels of ribosome biogenesis genes and two other components of TORC1 were higher in CcR1 compared to CcS1 under the same treatment, which suggested that the abundance of TORC1 in CcR1 was greater than in CcS1, leading to more active TORC1 signaling in CcR1. These results provided a better understanding about natural resistance of C. camelliae isolates to rapamycin and could help for developing new TORC1 signaling-targeting fungicides.

As a commonly used pesticide, the widespread use of terbuthylazine (TBA) may cause toxic effects in animals and human. However, the nephrotoxicity induced by TBA is unclear. Here, we explored the mechanism of TBA-induced nephrotoxicity through transcriptomics and molecular biology techniques in broilers. Pathologic analysis showed that TBA could cause renal cell vacuolation and fibrosis in broilers. Additionally, transcriptomic analysis showed that TBA can cause significant changes in the expression of some apoptosis-related genes, and GO and KEGG analysis also found that TBA can significantly change the functions of apoptosis pathway and AMPK signaling pathway in kidney. Subsequently, the protein expression levels of Bax, Bak-1, FADD, and cleaved Caspase-3/Caspase-3 were elevated significantly and the number of TUNEL-positive cells was increased markedly in kidney under TBA exposure. Meanwhile, we also found that TBA could activate AMPK/p53 pathway, as evidenced by the upregulated levels of AMPKα1 phosphorylation and protein expression of p53. Therefore, our results suggested that TBA could induce apoptosis via AMPK/p53 pathway in kidney. These findings identified the nephrotoxic mechanism of TBA through transcriptomics, providing a new insight into TBA toxicology.

The organophosphorus insecticide Chlorpyrifos (CPF) is widely used worldwide due to its high effectiveness. However, when ingested through the mouth and nose, it can cause severe neurotoxic effects and cognitive impairment. Natural anthocyanins show great potential in improving cognitive impairment. In this paper, we will delve into the protective effect of anthocyanins on CPF-induced cognitive impairment and its mechanism through the PI3K/Akt signaling pathway. Morris water maze, histopathological, ELISA and western blot analyses showed that anthocyanins effectively ameliorated CPF-induced spatial learning memory impairment in mice by ameliorating CPF-induced AChE inhibition, oxidative stress, and neuroinflammation and by modulating the levels of apoptosis (Caspase-3, Caspase-9) and autophagy (LC3II/ LC3I, Beclin1, p62, mTOR) biomarkers, in order to restore damaged hippocampal tissue morphology, neuron and synapse structures. To identify the action pathway of anthocyanins, we used KEGG and GO pathway enrichment analysis for screening prediction and western blot and molecular docking to verify that anthocyanins improve CPF-induced cognitive impairment by activating the PI3K/Akt pathway.

The brown planthopper (BPH), Nilaparvata lugens (Stål), is a notorious pest affecting Asian rice crops. The evolution of insecticide resistance in BPH has emerged as a significant challenge in effectively managing this pest. This study revealed the resistance status of BPH to nine insecticides in ten provinces and Shanghai City in China from 2020 to 2023. Monitoring results showed that the resistance of BPH to triflumezopyrim, nitenpyram, and dinotefuran increased rapidly. The average resistance ratio of BPH to triflumezopyrim increased from 2.5 to 7.1 fold, nitenpyram from 18.3 to 37.7 fold, and dinotefuran from 119.5 to 268.1 fold. All populations remained extremely high resistance to imidacloprid, thiamethoxam, and buprofezin. Most field populations of BPH maintained moderate resistance to chlorpyrifos and sulfoxaflor, and high resistance to pymetrozine by rice stem dipping method. However, considering the reproduction-inhibiting character of pymetrozine, susceptible to low resistance levels to pymetrozine were monitored by Insecticide Resistance Action Committee (IRAC) NO.005 method. This result indicated that pymetrozine might lose efficacy in the control of application generation, but it could significantly inhibit the reproduction of field populations of BPH. Additionally, we compared the expression levels of 11 nicotinic acetylcholine receptor (nAChR) genes, the targets of nAChR competitive modulators, in four field populations (FY23, YH23, LJ23, LP23) and susceptible strain. The expression level of nAChR α4 was significantly reduced in all field populations, while α1, α2, α6, and α7 were significantly reduced in some field populations. Our findings provide valuable information for resistance management strategies in N. lugens and offer new insights into the resistance mechanisms of nAChR competitive modulators.

The small brown planthopper (SBPH), Laodelphax striatellus, poses a significant threat to rice crops, necessitating innovative pest control strategies. This study evaluated the potential of validamycin A (Val A) and RNA interference (RNAi) targeting trehalase genes (LsTre1 and LsTre2) in controlling SBPH. Our results demonstrated that Val A treatment of rice seedlings led to a dose-dependent mortality of SBPH. Concurrently, Val A induced the upregulation of LsTre1 and LsTre2, suggesting a compensatory feedback mechanism. Furthermore, foliar-applied chimeric dsRNA targeting LsTre1 and LsTre2 exhibited higher insecticidal activity than individual dsLsTre1 and dsLsTre2 or mixed dsRNAs. Remarkably, co-application of Val A and chimeric dsRNA increased SBPH mortality due to the suppression of Val A-induced LsTre1 and LsTre2 upregulation by chimeric dsRNA. These results suggest that the co-application of Val A and chimeric dsRNA targeting trehalase genes could be an effective SBPH control strategy.

Thiacloprid (TCL), commonly known as Biscaya, is among the most widely used pesticides in agriculture, designed to eliminate insects by targeting their nicotinic receptors. This study explores the effects of orally administering TCL (at a dose of 50 mg/kg) on the hormone secretion crucial for pregnancy and the factors influencing abortion throughout the early, middle, and late stages of pregnancy in female rats. Following TCL exposure, there were significant increases in levels of 17β-Estradiol, prostaglandins F and E, and serum oxytocin hormone in different stages of pregnancy. In contrast, progesterone and endothelin-1 serum levels notably decreased during the initial and final stages of pregnancy. Additionally, TCL led to a substantial rise in lipid peroxidation levels and a decrease in total thiol molecules and total antioxidant capacity, especially in uterine tissue. Although TCL did not significantly affect the morphological characteristics of the delivered fetuses, it notably increased the number of abortions, especially during the second and third stages of pregnancy. In summary, our findings suggest that TCL elevates the risk of abortion in pregnant rats by disrupting the secretion of hormones crucial for fertility (such as 17β-Estradiol/progesterone) and by increasing the secretion of abortion-inducing hormones like prostaglandins and oxytocin. Furthermore, these effects may be associated with disruptions in the oxidant/antioxidant balance within the ovaries and uterus.

Profenofos, as a typical chiral organophosphorus pesticide, can cause various environmental problems and even endanger human health when used in excess. The toxicity of chiral profenofos was investigated through multispectral analysis, molecular docking, and density functional theory (DFT), employing human serum albumin (HSA) as the model protein. Fluorescence titration and lifetime measurements demonstrated that the interaction between chiral profenofos and HSA involves static quenching. Chiral profenofos forms a 1:1 complex with HSA at site II (subdomain IIIA), primarily driven by hydrophobic interactions and hydrogen bonds. Notably, the binding efficacy diminishes as temperature increases. Spectroscopic analyses confirm that chiral profenofos alters the microenvironment and structure of HSA, with the R-enantiomer exerting a greater impact than the S-enantiomer. Consequently, the toxicological implications of the R-profenofos is significantly more pronounced. Investigating the molecular-level toxic effects of chiral pesticides enhances the thoroughness of pesticide assessments, aids in understanding their distribution, metabolism, and associated risks, and facilitates the development of mitigation strategies.

Neonicotinoid insecticides (NNI) are agonists of insect nicotinic acetylcholine receptors (nAChR) that induce non-elucidate mechanisms of abnormal behavior in insects. In this work, we investigated the effects of sublethal doses of the neonicotinoid thiamethoxam (TMX) on neurochemical and physiological parameters in cockroaches. Sublethal doses of TMX (0.01-10 ng.g body mass) caused significant alterations in most of the neurophysiological parameters evaluated. TMX reduced sustained locomotor activity by 19.9-25.8 %, depending on the dose. Leg grooming activity increased by 124.5 ± 3.4 %, 158.7 ± 3.5 %, 168.3 ± 3.4 %, and 160.4 ± 3.4 % (mean ± SEM) with TMX doses of 0.01, 0.1, 1, and 10 ng.g, respectively. Exploratory activity was significantly reduced only at the lowest TMX dose (0.01 ng.g) - the time spent immobile increased from 30 % to ∼45 %, whereas none of the doses affected the walking speed. Treatment with TMX (0.01 ng.g) markedly reduced the olfactory sensitivity of the cockroaches and also reduced the mechanosensory action potential amplitude, rise time and decay time by 61.2 ± 19 %, 50 ± 4 %, and 76.8 ± 9.5 %, respectively. In semi-isolated heart preparations, TMX caused positive chronotropism (increases of 34.7 ± 15.9 %, 26.8 ± 7.8 %, 43.0 ± 16.5 %, and 19.0 ± 13.7 % for 0.01, 0.1, 1, and 10 ng of TMX, respectively). TMX attenuated the activity of glutathione-S-transferase by 35.1 ± 6.4 % at the highest dose tested (10 ng.g). TMX caused alterations in the metal ion content of cockroach brains that varied with the dose tested and the ion examined. These findings indicate that sublethal doses of TMX can interfere with normal neurological function in cockroaches and disrupt brain metal ion homeostasis.

Dopamine (DA) is the most abundant biogenic amine present in the insect central nervous system, and regulates multiple functions in physiology and behaviors through dopamine receptors (DARs). The small brown planthopper Laodelphax striatellus is an important agricultural pest and causes serious damage by transmitting diverse plant viruses, such as rice stripe virus (RSV). However, DARs have not yet been molecularly characterized in planthoppers, and their roles in virus infection and transmission remain largely unknown in insect vectors. In this study, we cloned four LsDARs (LsDOP1, LsDOP2, LsDOP3 and LsDopEcR) from L.striatellus. LsDARs share considerable sequence identity with their orthologous DARs, and cluster nicely with their corresponding receptor groups. The transcript levels of LsDARs varied in different developmental stages and adult tissues, with the highest expressions in the egg stage and in the brain. The expression levels of LsDARs were significantly higher in RSV-viruliferous L.striatellus. Knockdown of LsDOP2 and LsDOP3 significantly downregulated the expressions of viral genes of capsid protein (CP) and RNA3 segment (RNA3), while LsDOP1 knockdown upregulated their expressions. Silencing LsDopEcR upregulated and then downregulated CP and RNA3 expressions. Moreover, LsDOP2 and LsDOP3 knockdown significantly decreased the vertical transmission rates of RSV. Meanwhile, DA injection promoted RSV transmission and accumulation. We further demonstrated that silencing of LsDARs significantly altered the expressions of vitellogenin (LsVg) and Vg receptor (LsVgR). Furthermore, the reproduction performance of L.striatellus was reduced by LsDOP2 and LsDOP3 knockdown, but increased by LsDopEcR knockdown, and not affected by LsDOP1 silencing. These results provide critical information concerning the roles of DARs in virus transmission and reproduction in L.striatellus, and open the way for the development of innovative strategies for planthopper control.

Rice is an important agricultural crop that faces serious challenges from pathogens, pests, and weeds during growth stages. Meanwhile, these organisms would interact with each other to increase the level of destruction. The previous studies showed that barnyard grass (Echinochloa spp) could be used as a temporary host to increase infestation of small brown planthopper (SBPH, Laodelphax striatellus), which is one of the main polyphagous pests. Herbicides are widely used to control weeds that induce resistance development. However, little is known about the effects of increased weed resistance on insect species. In this study, we investigated the effect of quinclorac-resistant and sensitive biotypes of barnyard grass (Echinochloa crus-galli var. zelayensis; Echinochloa crus-pavonis Schult) and rice plants (Wuyujing 3) on the ecological fitness of SBPH and examined physiological indicators of plants and SBPH to explore the mechanism. Our results showed that the growth and reproduction of SBPH promoted significantly reared on quinclorac-resistant barnyard grass. From the perspectives of oxidative stress response, the activities of peroxidase (POD) increased and the activities of catalase (CAT), mixed-functional oxidase (MFO), and carboxylesterase (CarE) decreased in SBPH reared on resistant barnyard grass. Combined with the increased amino acid contents (threonine, serine, methionine, and alanine) of resistant barnyard grass E. crus-pavonis, we speculate that quinclorac-resistant barnyard grass probably provides SBPH with a more suitable environment, thus increasing the risk of SBPH.

Excessive and unnecessary immune responses cause serious adverse effects due to self-tissue damage and energy consumption, particularly at the late stage of infection to terminate the induced immunity. Unlike mammals, which use long-chain fatty acid oxylipins, C18 oxygenated polyunsaturated fatty acids are suggested to act as immune resolvins in insects, including two epoxyoctadecamonoenoic acids (9,10-EpOME and 12,13-EpOME). This study investigated the physiological roles of EpOMEs in immune resolution in the lepidopteran insect, Maruca vitrata. The levels of two EpOMEs in the larvae increased during the late infection stage upon immune challenge. At their peak concentrations at 96 h post-infection (pi), both EpOMEs were found at similar levels: 323.18 pg/mg body weight for 9,10-EpOME and 322.07 pg/mg body weight for 12,13-EpOME. Both EpOMEs inhibited cellular and humoral immune responses, with 12,13-EpOME being more potent than 9,10-EpOME. Genes associated with EpOME synthase and degradation, identified as Mv-CYP1 and Mv-sEH, were detected in various developmental stages and tissues of M. vitrata. RNA interference (RNAi) targeting Mv-CYP1 failed to inhibit the immune response, whereas RNAi targeting Mv-sEH enhanced the immunosuppression. In contrast to the acute (< 12 h pi) immune response involving eicosanoid biosynthesis, the expression of these two genes linked to EpOME metabolism increased significantly at the late infection stage (> 12 h pi). Several alkoxide analogs of EpOME, with the epoxide group replaced by an alkoxide group, were synthesized; one such derivative demonstrated substantially greater efficacy than the natural EpOMEs in inhibiting the immune response. Additionally, using EpOME alkoxide significantly increased the effectiveness of microbial insecticides. Moreover, exposing young larvae to sublethal doses of EpOME alkoxide or sEH inhibitor induced severe developmental delays. These results suggest a novel strategy for insect pest control using insect immune resolvin analogs.

The application of Bacillus thuringiensis (Bt) has brought environmental benefits and delayed resistance development of pests. Most studies focus on the Bt insecticidal activity against pests, however, the molecular mechanism of Bt on impairing the growth and development of Spodoptera exigua remains unknown. Here, we show that juvenile hormone (JH) inhibits the lipogenesis mediated by fatty acid synthases (Fas) of S. exigua in response to Bt infection. The weight and lipid accumulation of S. exigua larvae post Bt infection were less than those of larvae without Bt infection. We further demonstrated that Bt infection causes the JH titer with a significant increase, which downregulates the expression of lipogenesis-related genes, SeFas3, SeFas4, and SeFas5, resulting in the delayed development of S. exigua larvae. In addition, the expression levels of SeFas genes were regulated by SeACC, indicating that SeFas genes were modulated by multiple pathways. Our findings reveal that novel insights into the molecular mechanisms underlying the impaired development caused by Bt infection which can inform the development of strategies for the sustainable pest control in the future.