Storage protein SfSP8 mediates larval starvation tolerance of Spodoptera frugiperda.

BACKGROUND: Energy homeostasis is vital for insects to survive food shortages. This study investigated the starvation tolerance of Spodoptera frugiperda, which invaded China in 2019, focusing on its storage protein family, crucial for energy balance. 10 storage protein family members were identified and their expression patterns at different development stages and under different starvation stress were analyzed. METHODS AND RESULTS: We used qPCR to evaluate the expression levels of storage protein family members under various larval instars and starvation conditions. We discovered that, among above 10 members, only 2 storage proteins, SfSP8 and SfSP7 showed significant upregulation in response to starvation stress. Notably, SfSP8 upregulated markedly after 24 h of fasting, whereas SfSP7 exhibited a delayed response, with significant upregulation observed only after 72 h of starvation. Then we significantly reduced the starvation tolerance of larvae through RNAi-mediated knockdown of SfSP8 and also altered the starvation response of SfSP7 from a late to an early activation pattern. Finally, we constructed transgenic Drosophila melanogaster with heterologous overexpressing SfSP8 revealed that the starvation tolerance of the transgenic line was significantly stronger than that of wild-type lines. CONCLUSIONS: SfSP8 was the core storage protein member that mediated the starvation tolerance of larvae of S. frugiperda. Our study on the novel function of storage proteins in mediating larval starvation tolerance of S. frugiperda is conducive to understanding the strong colonization of this terrible invasive pest.

The transcriptomic profile of Spodoptera frugiperda differs in response to a novel insecticide, cyproflanilide, compared to chlorantraniliprole and avermectin.

BACKGROUND: Cyproflanilide is a novel chemical that is already undergoing insecticide registration in China and has been categorized as a member of group 30 by the IRAC. Since it was first detected in 2019, the fall armyworm (FAW), Spodoptera frugiperda, has become a serious pest in China. Our laboratory and field efficacy trials indicated that cyproflanilide exhibits high larvicidal activity against FAW. However, the effect of cyproflanilide against FAW remains unknown. And it is worth exploring further before the cyproflanilide becomes commercially available. RESULTS: We found larvae exposed to cyproflanilide had significantly shorter body length and higher death rates compared to control larvae. Additionally, we found surviving larvae had a significantly longer developmental period compared to control larvae. The potential molecular mechanisms of cyproflanilide against FAW were investigated using comparative transcriptomic analyses on larval samples subjected to three insecticide treatments, including cyproflanilide and two other commonly used insecticides against FAW in China, chlorantraniliprole and avermectin. We found that several subunits of the γ-aminobutyric acid receptor (GABAR), a possible target protein of cyproflanilide, were significantly up-regulated at the transcriptional level during cyproflanilide-induced stress. Additionally, between the control and cyproflanilide-treated samples, we identified 131 differentially expressed genes (DEGs) associated with detoxification metabolism. Of these, we found four P450 genes that were significantly up-regulated under cyproflanilide stress but were not DEGs when exposed to chlorantraniliprole and avermectin, or 23 other pesticides from previous reports. Furthermore, we discovered an interesting gene aggregation region for insect cuticle proteins (CPs) on the 18th chromosome, which is likely related to FAW cross-resistance to cyproflanilide and avermectin. CONCLUSIONS: Our results contribute to a greater understanding of the mechanisms by which cyproflanilide affects FAW. Additionally, we identified the similarities and differences in transcriptomic profiling of FAW between the novel insecticide cyproflanilide and two other commonly used insecticides.

The effect of chlorantraniliprole on the transcriptomic profile of Spodoptera frugiperda: a typical case analysis for the response of a newly invaded pest to an old insecticide.

BACKGROUND: Chlorantraniliprole is a diamide insecticide widely used in China over the last 15 years. The fall armyworm (FAW), Spodoptera frugiperda, newly invaded China in 2019. The response of FAW to chlorantraniliprole deserves more attention, in the context of many destructive lepidopteran species are resistant to diamide insecticides and the patent on core chemical of chlorantraniliprole in China expired in August 2022. METHODS AND RESULTS: This study investigated the response profile in larvae under chlorantraniliprole-induced (LC50) stress using methods of bioassay, RNA-Seq and qPCR. We observed growth inhibition and lethal effects in FAW larvae, but at a relatively high LC50 value compared to other several pests. Additionally, under chlorantraniliprole-induced stress, 3309 unigenes were found to be differentially expressed genes. The impacted genes included 137 encoding for detoxification enzymes, 29 encoding for cuticle proteins, and 20 key enzymes involved in the chitin metabolism, which all associated with metabolic resistance. Finally, we obtained the single nucleotide polymorphisms (SNPs) of two RyR genes, which are the target proteins for chlorantraniliprole. We also investigated the causes of the high LC50 value in our FAW, which possibly related to the stabilized 4743 M on SNP frequency of RyR. These findings documented the genetic background of RyR of FAW and indicated that application of chlorantraniliprole has a high risk of controlling FAW in China. CONCLUSION: In brief, our results provide a better understanding of the mechanisms of chlorantraniliprole toxicity and detoxification in FAW, and will aid in monitoring the development of resistant strains for a newly pest to an old insecticide.

Transcriptomic Analysis Reveals the Detoxification Mechanism of Chilo suppressalis in Response to the Novel Pesticide Cyproflanilide.

Chilo suppressalis is one of the most damaging rice pests in China's rice-growing regions. Chemical pesticides are the primary method for pest control; the excessive use of insecticides has resulted in pesticide resistance. C. suppressalis is highly susceptible to cyproflanilide, a novel pesticide with high efficacy. However, the acute toxicity and detoxification mechanisms remain unclear. We carried out a bioassay experiment with C. suppressalis larvae and found that the LD10, LD30 and LD50 of cyproflanilide for 3rd instar larvae was 1.7 ng/per larvae, 6.62 ng/per larvae and 16.92 ng/per larvae, respectively. Moreover, our field trial results showed that cyproflanilide had a 91.24% control efficiency against C. suppressalis. We investigated the effect of cyproflanilide (LD30) treatment on the transcriptome profiles of C. suppressalis larvae and found that 483 genes were up-regulated and 305 genes were down-regulated in response to cyproflanilide exposure, with significantly higher CYP4G90 and CYP4AU10 expression in the treatment group. The RNA interference knockdown of CYP4G90 and CYP4AU10 increased mortality by 20% and 18%, respectively, compared to the control. Our results indicate that cyproflanilide has effective insecticidal toxicological activity, and that the CYP4G90 and CYP4AU10 genes are involved in detoxification metabolism. These findings provide an insight into the toxicological basis of cyproflanilide and the means to develop efficient resistance management tools for C. suppressalis.

FAR knockout significantly inhibits Chilo suppressalis survival and transgene expression of double-stranded FAR in rice exhibits strong pest resistance.

Chilo suppressalis is one of the most prevalent and damaging rice pests, causing significant economic losses each year. Chemical control is currently the primary method of controlling C. suppressalis. However, the indiscriminate use of chemical insecticides increases pest resistance, pollutes the environment and poses a significant health threat to humans and livestock, highlighting the need to find safer, more pest-specific and more effective alternatives to pest control. Plant-mediated RNA interference (RNAi) is a promising agricultural pest control method that is highly pest-specific and has less of an impact on the environment. Using multi-sgRNAs/Cas9 technology to delete Fatty acyl-CoA reductase (FAR) of C. suppressalis in the G0 generation, we show that downregulating FAR transcription may significantly increase the mortality rate and darken the epidermis of C. suppressalis compared with the control. Subsequently, we developed dsFAR transgenic rice lines using Agrobacterium-mediated genetic transformation and then screened three strains expressing dsFAR at high levels using transcriptional level analysis. Using transgenic rice stems, a laboratory feeding bioassay indicated that at least one line (L#10) displayed a particularly high level of insect resistance, with an insect mortality rate of more than 80%. In the field trials, dsFAR transgenic rice displayed high levels of resistance to C. suppressalis damage. Collectively, these results suggest the potential of a new environment-friendly, species-specific strategy for rice pest management.

RNA interference knockdown of insulin receptor inhibits ovarian development in Chilo suppressalis.

BACKGROUND: The nutritional signaling pathway regulates an insect's size, development, and lifespan, as well as playing a vital role in reproduction. The insulin/insulin-like growth factor signaling (IIS) pathway plays a key role in the nutrition signaling pathway. As an integral component of the IIS pathway, insulin receptor (InR), a receptor tyrosine kinase, plays a role in the insulin pathway by controlling reproduction in many insect species. However, the precise molecular function of InR in non-model insect reproduction is poorly understood. METHODS: In our study, Chilo suppressalis, a well-known rice pest, was used as a molecular system to determine the role of InR in insect reproduction. Sequencing the InR gene of C. suppressalis, comparing the amino acid sequence-specific structure, and constructing a phylogenetic tree revealed that this gene has four main domains: ligand binding L domain, Furin-like region, fibronectin type III domains, and Tyrosine kinase catalytic domain, which were all highly conserved in insects. RESULTS: By characterizing the spatiotemporal expression profile of InR in different developmental stages and tissues, we found that InR gene expression was highest on the 3-day old in female pupae, 6th instar larvae, and fat body on the 6-day old in female pupae. InR gene expression may promote the molting and pupation of larvae and play a role in reproduction in the fat body. Furthermore, the RNA interference knockdown of InR dramatically reduced yolk deposition and blocked oocyte maturation. After suppression of InR, the expression of several other genes fluctuated to varying degrees. CONCLUSION: In conclusion, InR is vital to reproduction and is expected to become a new target for pest management.

A New Lignan and C(6)-Oxygenated Flavonoids from the Inflorescence of Ambrosia artemisiifolia.

A new lignan (4,4',5'-trihydroxy-5,3'-dimethoxy-3-O-9',2-(7'R)-lignan, 1) and eight C(6)-oxygenated flavonoids (2-9), including a newly identified flavonoid (7,3',4'-trihydroxy-3,5,6-trimethoxyflavone, 2), were isolated from the inflorescence of Ambrosia artemisiifolia L. The structures of these isolates were determined using extensive spectroscopic analyses and comparison with data previously reported in the literature. The absolute configuration of compound 1 was established using electronic circular dichroism (ECD) spectrum. All the flavonoids (2-9) showed inhibitory effects on LPS-induced NO production in RAW264.7 cells, with the inhibition rate ranging from 24.51 % to 69.82 % at 50 µM. The in vitro cytotoxicity study showed that compounds 3-8 have a 60 % inhibition rate against SMMC-7721 at a concentration of 40 µM, while compounds 5 and 8 also exhibited inhibitory activity against HL-60 at 40 µM with the inhibition rate of 83.36 % and 52.01 %, respectively.

Sesquiterpenoids from the Inflorescence of Ambrosia artemisiifolia.

The successful invasion of Ambrosia artemisiifolia is largely due to allelopathy. As an invasive alien plant, A. artemisiifolia has spread rapidly in Asia and Europe. Studies have shown that sesquiterpenoids play an important role in plant allelopathy. However, it is unclear whether the inflorescence of A. artemisiifolia also contains allelopathic components. In this paper, our phytochemical research focuses on the inflorescence of A. artemisiifolia. Twenty sesquiterpenoids, including four new ones (1-4) were isolated through successive chromatographic columns and identified by spectroscopic methods. At a concentration of 200 µg/mL, all the compounds tested were evaluated for their allelopathic activities on seedling growth of wheat. Our results indicate that nine compounds inhibited both the root and shoot growth of seedlings. Compounds 14, 15, 17, and 20 significantly inhibited root length, which was more than 50% shorter than the control. This study identified the chemical profile of the sesquiterpenoids occurring in the inflorescence of A. artemisiifolia. The bioactivity screening results provide further understanding of the chemical basis of allelopathy in A. artemisiifolia.

Molecular characterization of the Krüppel-homolog 1 and its role in ovarian development in Sogatella furcifera (Hemiptera: Delphacidae).

Juvenile hormone (JH) plays a pivotal role in insect reproduction. The Krüppel-homolog 1 (Kr-h1) is a JH-inducible zinc finger transcription factor that has also been found to play a role in insect reproduction, however, its function varies across species. In this study, we cloned SfKr-h1 from Sogatella furcifera and investigated its role in ovarian development. The open reading frame of SfKr-h1 is 1 800 bp encoding 599 amino acids. The putative amino acid sequence of SfKr-h1 contains eight putative C2H2-type zinc finger domains and is highly homologous with the Kr-h1s of other hemipteran species. Expression of SfKr-h1 peaked 96 h after adult emergence and was highest in the ovary. RNA interference (RNAi) knockdown of SfKr-h1 substantially reduced the transcription of SfVg, and arrested ovarian development. These results suggest that SfKr-h1 is critical for normal ovarian development in S. furcifera.

Genetic diversity and differentiation of populations of Chlorops oryzae (Diptera, Chloropidae).

BACKGROUND: Chlorops oryzae is an important pest of rice crops. There have been frequent outbreaks of this pest in recent years and it has become the main rice pest in some regions. To elucidate the molecular mechanism of frequent C. oryzae outbreaks, we estimated the genetic diversity and genetic differentiation of 20 geographical populations based on a dataset of ISSR markers and COI sequences. RESULTS: ISSR data revealed a high level of genetic diversity among the 20 populations as measured by Shannon's information index (I), Nei's gene diversity (H), and the percentage of polymorphic bands (PPB). The mean coefficient of gene differentiation (Gst) was 0.0997, which indicates that only 9.97% genetic variation is between populations. The estimated gene flow (Nm) value was 4.5165, indicating a high level of gene flow and low, or medium, genetic differentiation among some populations. The results of a Mantel test revealed no significant correlation between genetic and geographic distance among populations, which means there is no evidence of significant genetic isolation by distance. An UPGMA (unweighted pair-group method with arithmetic averages) dendrogram based on genetic identity, did not indicate any major geographic structure for the 20 populations examined. mtDNA COI data indicates low nucleotide (0.0007) and haplotype diversity (0.36) in all populations. Fst values suggest that the 20 populations have low, or medium, levels of genetic differentiation. And the topology of a Neighbor-Joining tree suggests that there are no independent groups among the populations examined. CONCLUSIONS: Our results suggest that C. oryzae populations have high genetic diversity at the species level. There is evidence of frequent gene flow and low, or medium, levels of genetic differentiation among some populations. There is no significant correlation between genetic and geographic distance among C. oryzae populations, and therefore no significant isolation by distance. All results are consistent with frequent gene exchange between populations, which could increase the genetic diversity, and hence, adaptability of C. oryzae, thereby promoting frequent outbreaks of this pest. Such knowledge may provide a scientific basis for predicting future outbreaks.

New Cyclic Diarylheptanoids from Platycarya strobilacea.

Five new cyclic diarylheptanoids (platycary A-E, compounds 1-5) and three previously identified analogues (i.e., phttyearynol (compound 6), myricatomentogenin (compound 7), and juglanin D (compound 8)) were isolated from the stem bark of Platycarya strobilacea. The structures of these compounds were determined using NMR, HRESIMS, and electronic circular dichroism (ECD) data. The cytotoxicity of compounds 1-5 and their ability to inhibit nitric oxide (NO) production, as well as protect against the corticosterone-induced apoptosis of Pheochromocytoma (PC12) cells, were evaluated in vitro using the appropriate bioassays. Compounds 1 and 2 significantly inhibited the corticosterone-induced apoptosis of PC12 cells at a concentration of 20 µΜ.

Evaluation of reference genes and expression of key genes involved in the isoprenoid metabolic pathway of rice leaves after infection by the Southern rice black-streaked dwarf virus.

The Southern rice black-streaked dwarf virus (SRBSDV), a novel Fijivirus, poses a major threat to rice production in East Asia. Analysis of the gene expression of SRBSDV-infected rice plants may reveal the molecular basis of interactions between the virus, its vector and rice plants. Reliable reference genes are required for accurate qRT-PCR analysis. However, no reliable, valid reference genes for examining gene expression in SRBSDV-infected rice plants have so far been identified. We examined the expression of eight candidate reference genes in the leaves of SRBSDV-infected, and healthy, rice plants at different points in time after virus inoculation. We used four dedicated algorithms, geNorm, BestKeeper, NormFinder and RefFinder, to evaluate the performance of these candidate genes. The RefFinder results indicate that 18S, EF1α and UBQ10 are suitable reference genes. In addition, we used these three reference genes to analyze the expression of key genes involved in the isoprenoid metabolic pathway in rice leaves after infection by SRBSDV. The results of this analysis reveal that SRBSDV may suppress the production of the rice plant volatiles that attract natural enemies of its vector Sogatella furcifera, thereby increasing the likelihood of pathogen transmission.

Knockdown of Methoprene-Tolerant Arrests Ovarian Development in the Sogatella furcifera (Hemiptera: Delphacidae).

Juvenile hormone (JH) is responsible for repressing larval metamorphosis and inducing vitellogenesis and egg production in insects. Methoprene-tolerant (Met) is known to be an intracellular receptor and transducer of JH. We examined the role of Met in ovarian development in the rice pest Sogatella furcifera (Horváth). We first cloned and sequenced S. furcifera Met (SfMet). The SfMet protein belongs to the basic helix-loop-helix/Per-Arnt-Sim (bHLH-PAS) family with a bHLH domain and two PAS domains (PAS-A and PAS-B). SfMet was expressed in all developmental stages and tissues but was most highly expressed in the ovaries of adult females. Furthermore, RNA interference (RNAi) mediated silencing of SfMet substantially reduced the expression of SfVg, decreased yolk protein deposition and blocked oocyte maturation and ovarian development. These results demonstrate that SfMet plays a key role in female reproduction in S. furcifera and suggest that targeting this gene could be an effective way of controlling this pest.

Transcriptomics reveal the molecular underpinnings of chemosensory proteins in Chlorops oryzae.

BACKGROUND: Chemosensory proteins are a family of insect-specific chemical sensors that sense specific chemical cues and regulate insect behavior. Chemosensory proteins have been identified and analyzed in many insect species, such as Drosophila melanogaster, Bactrocera dorsalis and Calliphora stygia. This research has revealed that these proteins play a crucial role in insect orientation, predation and oviposition. However, little is known about the chemosensory proteins of Chlorops oryzae, a major pest of rice crops throughout Asia. RESULTS: Comparative transcription analysis of the genes of Chlorops oryzae larvae, pupae and adults identified a total of 104 chemosensory genes, including 25 odorant receptors (ORs), 26 odorant-binding proteins (OBPs), 19 ionotropic receptors (IRs), 23 gustatory receptors (GRs) and 11 sensory neuron membrane proteins (SNMPs). The sequences of these candidate chemosensory genes were confirmed and used to construct phylogenetic trees. Quantitative real-time PCR (qRT-PCR) confirmed that the expression of candidate OR genes in different developmental stages was consistent with the fragments per kilobase per million fragments (FPKM) values of differentially expressed genes (DEGs). CONCLUSIONS: The identification of chemosensory genes in C. oryzae provides a foundation for the investigation of the function of chemosensory proteins in this species, which, in turn, could allow the development of new, improved methods of controlling this pest.

New 30-Noroleanane Triterpenoid Saponins from Holboellia coriacea Diels.

Three new 30-noroleanane triterpenoid saponins, akebonoic acid 28-O-ß-d-glucopyranosyl-(1''→6')-ß-d-glucopyranosyl ester (1), akebonoic acid 28-O-(6''-O-caffeoyl)-ß-d-glucopyranosyl-(1''→6')-ß-d-glucopyranosyl ester (Holboelliside A, 2) and 3ß,20α,24-trihydroxy-29-norolean-12-en-28-oic acid 3-O-(6'-O-caffeoyl)-ß-d-glucopyranoside (Holboelliside B, 3) were isolated from the stems of Holboellia coriacea Diels, together with five known compounds, eupteleasaponin VIII (4), 3α-akebonoic acid (5), quinatic acid (6), 3ß-hydroxy-30-norhederagenin (7) and quinatoside A (8). The structures of these compounds were determined on the basis of spectral and chemical evidence. Compounds 1-5 were evaluated for their inhibitory activity against three human tumors HepG2, HCT116 and SGC-7901 cell lines in vitro.

Sequence analysis of mitochondrial ND1 gene can reveal the genetic structure and origin of Bactrocera dorsalis s.s.

BACKGROUND: The oriental fruit fly, Bactrocera dorsalis s.s., is one of the most important quarantine pests in many countries, including China. Although the oriental fruit fly has been investigated extensively, its origins and genetic structure remain disputed. In this study, the NADH dehydrogenase subunit 1 (ND1) gene was used as a genetic marker to examine the genetic diversity, population structure, and gene flow of B. dorsalis s.s. throughout its range in China and southeast Asia. RESULTS: Haplotype networks and phylogenetic analysis indicated two distinguishable lineages of the fly population but provided no strong support for geographical subdivision in B. philippinensis. Demographic analysis revealed rapid expansion of B. dorsalis s.s. populations in China and Southeast Asia in the recent years. The greatest amount of genetic diversity was observed in Manila, Pattaya, and Bangkok, and asymmetric migration patterns were observed in different parts of China. The data collected here further show that B. dorsalis s.s. in Yunnan, Guangdong, and Fujian Provinces, and in Taiwan might have different origins within southeast Asia. CONCLUSIONS: Using the mitochondrial ND1 gene, the results of the present study showed B. dorsalis s.s. from different parts of China to have different genetic structures and origins. B. dorsalis s.s. in China and southeast Asia was found to have experienced rapid expansion in recent years. Data further support the existence of two distinguishable lineages of B. dorsalis s.s. in China and indicate genetic diversity and gene flow from multiple origins.The sequences in this paper have been deposited in GenBank/NCBI under accession numbers KC413034-KC413367.

The CsmiR1579-CsKr-h1 module mediates rice stem borer development and reproduction: An effective target for transgenic insect-resistant rice.

The rice stem borer (RSB, Chilo suppressalis) is a significant agricultural pest that mainly depends on chemical control. However, it has grown to varied degrees of pesticide resistance, which poses a severe threat to rice production and emphasizes the need for safer, more efficient alternative pest management strategies. Here, in vitro and in vivo experiments analyses reveal miR-1579 binds to the critical transcription factor Krüppel homologue 1 (Kr-h1) and negatively regulates its expression. Overexpression of miR-1579 in larvae with significantly lower levels of Kr-h1 was associated with a decline in larval growth and survival. Furthermore, in female pupae, miR-1579 overexpression led to abnormalities in ovarian development, suggesting that targeting miR-1579 could be a potential management strategy against C. suppressalis. Therefore, we generated transgenic rice expressing miR-1579 and screened three lines that had a single copy of highly abundant mature miR-1579 transcripts. Expectedly, fed with transgenic miR-1579 rice lines were significantly lower survival rates in larvae and high levels of resistance to damage caused by C. suppressalis infestation. These findings suggest that miRNA-mediated RNAi could provide an effective and species-specific strategy for C. suppressalis control.

Molecular cloning, expression, and characterization of a putative activation-associated secreted protein from Angiostrongylus cantonensis.

Activation-associated secreted protein (ASP) had been found in many helminthes, which was associated with pathogenesis and stage transition. A complementary DNA (cDNA) sequence encoding a putative two-domain ASP was obtained from an Angiostrongylus cantonensis fourth-stage larvae cDNA library, which we designated as AgASP. The cDNA of AgASP contains an open reading frame encoding 424 amino acids, the first 19 residues being a putative secretion signal. The expression pattern of this protein was investigated by real-time polymerase chain reaction and Western blot. We found that this protein expressed most highly in the brain-stage larvae (Lbr) of this parasite and existed in the excretory/secretory products of this stage. Immunofluorescence showed it existed in the lumen of the Lbr. The recombinant protein can be recognized by the infection sera from mice (nonpermissive host), while it cannot be recognized by infection sera from rats (permissive host). The infiltration of neutrophils in infected nonpermissive host can be lessened by immunizing this host with this protein (immunized vs control group, 13.7 ± 10.2 vs 65.5 ± 19.2). These findings suggest that this protein plays a role in the pathogenesis of human angiostrongyliasis and is worthy of further study.

Cytochrome P450s genes CYP321A9 and CYP9A58 contribute to host plant adaptation in the fall armyworm Spodoptera frugiperda.

BACKGROUND: The fall armyworm, Spodoptera frugiperda is one of the most destructive agricultural pests, which can complete their entire life cycle on various plants. At present, some detoxification genes have been proved to be involved in the adaptability to plants in insects. However, the genetics behind insect pest responses to host switches, and their ability to adapt to new host plants, remain poorly understood. This study was conducted to evaluate the adaptation of S. frugiperda to host plant and determine the roles of CYP321A9 and CYP9A58 in the detoxification metabolism of the fall armyworm. RESULTS: The results revealed that feeding on maize was more suitable for S. frugiperda to develop compared with rice. In addition, knocking down of SfCYP321A9 and SfCYP9A58 resulted in a prolonged developmental time of S. frugiperda larvae that fed on rice. Meanwhile, RNAi knockdown of SfCYP321A9 resulted in significantly higher mortality of S. frugiperda larvae when exposed to the rice allelochemicals, ferulic acid, gramine and tricin. Furthermore, overexpression of SfCYP321A9 significantly reduced mortality in Drosophila melanogaster when exposed to gramine and tricin. CONCLUSION: Our results suggest that CYP321A9 and CYP9A58 genes play a key role in host plant adaptation in S. frugiperda, which contribute to a greater understanding of the molecular basis of host plant adaptation and provide the means to develop effective management tools for S. frugiperda resistance. © 2023 Society of Chemical Industry.

Function analysis of CYP321A9 from Spodoptera frugiperda (Lepidoptera: Noctuidae) associated with emamectin benzoate, and a novel insecticide, cyproflanilide detoxification.

The fall armyworm, Spodoptera frugiperda, is an invasive agricultural pest that is a serious threat to agricultural production and global food security. Chemical control is the most effective method for preventing outbreaks of S. frugiperda. However, insecticide resistance often develops as a result of prolonged pesticide use, and the molecular mechanisms involved in insecticide resistance remain unclear. Insect cytochrome P450 monooxygenases play an important role in the detoxification of insecticides and insecticide resistance in Lepidoptera. In our study, the LC50 of a novel insecticide (cyproflanilide) and a conventional insecticide (emamectin benzoate) for S. frugiperda second-instar larvae were 7.04 and 1.61 mg/L, respectively. Furthermore, CYP321A9 expression was upregulated in larvae exposed to these insecticides. Additionally, knockdown of CYP321A9 by feeding larvae with dsRNA for 72 h significantly increased the mortality of S. frugiperda exposed to emamectin benzoate and cyproflanilide by 23.33% and 7.78%, respectively. Our results indicate that CYP321A9 may play an important role in the detoxification of emamectin benzoate and cyproflanilide in S. frugiperda. Our findings provide a basis to better understand the mechanisms of insecticide resistance and contribute to the control of S. frugiperda.