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.

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.

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.

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.

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.

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.

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.

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.

A chromosome-level genome assembly provides insights into the environmental adaptability and outbreaks of Chlorops oryzae.

Chlorops oryzae is a pest of rice that has caused severe damage to crops in major rice-growing areas in recent years. We generated a 447.60 Mb high-quality chromosome-level genome with contig and scaffold N50 values of 1.17 Mb and 117.57 Mb, respectively. Hi-C analysis anchored 93.22% scaffolds to 4 chromosomes. The relatively high expression level of Heat Shock Proteins (HSPs) and antioxidant genes in response to thermal stress suggests these genes may play a role in the environmental adaptability of C. oryzae. The identification of multiple pathways that regulate reproductive development (juvenile hormone, 20-hydroxyecdsone, and insulin signaling pathways) provides evidence that these pathways also play an important role in vitellogenesis and thus insect population maintenance. These findings identify possible reasons for the increased frequency of outbreaks of C. oryzae in recent years. Our chromosome-level genome assembly may provide a basis for further genetic studies of C. oryzae, and promote the development of novel, sustainable strategies to control this pest.

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.

Tangnaikang Alleviates Hyperglycemia and Improves Gut Microbiota in Diabetic Mice.

Dysregulation of gut microbiota contributes to the development of type 2 diabetes. To investigate the antidiabetic effect of Tangnaikang and its regulation of gut microbiota in diabetic KKAy mice, a type 2 diabetes mouse model was established by feeding KKAy mice with a high-fat diet (HFD) for 2 weeks. The diabetic KKAy mice were treated with vehicle, Acarbose, or different doses of Tangnaikang once a day for 8 weeks. The fasting plasma glucose (FPG) levels and bodyweights were measured weekly. The fecal and blood samples were collected 8 weeks after treatment. The 16s rRNA sequencing and bioinformatics analysis were conducted to explore the effects of Tangnaikang treatment on the richness, diversity, and relative abundance of gut microbiota. Compared with other treatments, high-dose Tangnaikang (4.68 g/kg) significantly reduced FPG levels while elevating bodyweights in model mice. Compared with saline treatment, different doses of Tangnaikang significantly increased gut microbial species richness and diversity. Linear discriminant analysis effect size identified potential bacterial biomarkers associated with Tangnaikang treatment. Relative abundance analysis revealed that Tangnaikang treatment modulated the abundance of gut bacteria at the class and genus levels, such as Bacilli, Lactobacillus, and Alistipes. The principal component analysis demonstrated that, compared with the samples of the high-dose group, the samples of medium-dose and low-dose groups were closer to those of the model group. Tangnaikang alleviated hyperglycemia and improved the composition and abundance of gut microbiota in diabetic KKAy mice.

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.

Identification and phylogenetics of Spodoptera frugiperda chemosensory proteins based on antennal transcriptome data.

Understanding the interaction between the insect olfactory system and the environment is crucial for fully explaining the molecular mechanisms underlying insect behavior, and providing new strategies for integrated pest management. Although there is good evidence that olfactory proteins play a vital role in mediating insect behaviors, the olfactory mechanism of insects remains poorly understood. We identified a total of 71 chemosensory genes; 25 odorant-binding proteins (OBPs), 27 odorant receptors (ORs), 8 ionotropic receptors (IRs), 8 chemosensory proteins (CSPs) and 3 sensory neuron membrane proteins (SNMPs), in the antennae of male and female fall armyworms, Spodoptera frugiperda, an invasive global pest that causes significant economic damage worldwide. We used differential gene expression (DGE) and fragments per kilobase per million fragments (FPKM) values to compare the transcript levels of candidate chemosensory genes, and qRT-PCR to compare the expression levels of the OR gene, in male and female antennae. The expression of candidate OR genes in male and female antennae was consistent with the DGE data, and the expression of the SfruCL4419.Contig1-All and SfruUnigene1070-All genes was sex-biased. These results not only provide new information on the olfactory mechanism of S. frugiperda, and insects in general, but also suggest new gene targets for pest control.

A novel negative thermotaxis behavior in rice planthoppers is regulated by TRPA1 channel.

BACKGROUND: In the field, we observed that many white-backed planthoppers (Sogatella furcifera, WBPHs) stayed in the top region of rice plants exposed to direct sunshine. It was known that WBPHs frequently took flight when the ground temperature was about 25 °C, then climbed to and flew in a dense layer corresponding to an air temperature of about 16 °C in the sky. Its migration height was higher than the top of the surface temperature inversion. It is still unclear whether WBPHs prefer warm or cold regions, and therefore we studied the thermal responses of WBPHs and other insects using a simulated system. RESULTS: We found that WBPHs preferred a cold region to a warm one, unexpectedly below their comfort temperature zone. After comparative analysis with other insect species, such as small brown planthoppers, brown planthoppers, Trialeurodes vaporariorum (stinkbugs, a predator of planthoppers) and Bemisia tabaci (whitefly), only three planthoppers showed cold preference behavior. RNA interference experiments revealed that this behavior of WBPHs can be regulated by the transient receptor potential (TRP) channels TRPA1 channel. Furthermore, podocarpic acid, an agonist of TRPA1, weakened the cold preference, whereas A-967079, an antagonist of TRPA1, had the opposite effect. CONCLUSION: We reported a novel cold preference (negative thermotaxis) in rice planthoppers that was regulated in WBPHs by the TRPA1 channel. Cold preference of rice planthoppers is probably related to its choice behavior of the special migratory temperature layer. Our results expanded a new perspective to develop novel strategies for behavioral manipulation and management of rice planthoppers. © 2020 Society of Chemical Industry.

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.

A new epicatechin glucopyranoside derivative from Styrax suberifolius.

A new derivative of epicatechin glucopyranoside, (2R,3R)-3,7,4'-trihydroxy-5,3'-dimethoxyflavan 7-O-ß-d-glucopyranoside (1), together with three mononuclear phenolic acid esters, methyl orsellinate (2), ethyl orsellinate (3) and methyl ß-orcinolcarboxylate (4) were isolated from the bark of Styrax suberifolius. The structures of 1-4 were determined on the basis of extensive analysis of NMR and MS spectra combined with chemical hydrolysis. The antifungal activities of the isolated compounds against three plant pathogenic fungi, Alternaria solani, Fusarium oxysporum and Phomopsis cytospore were evaluated using radial growth inhibition assay. Compounds 2, 3 and 4 exerted selective inhibitory activities against the tested fungi. Among of them, methyl ß-orcinolcarboxylate (4) exhibited obvious inhibitory effect against P. cytospore, with an inhibition rate of 86.72% at 100 µg/ml.

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.

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.

A Microinjection Method for Infecting the Planthopper Sogatella furcifera (Hemiptera: Delphacidae) with the Southern Rice Black-Streaked Dwarf Virus.

The southern rice black-streaked dwarf virus (SRBSDV) causes significant economic damage to rice crops. This virus is transmitted to rice plants by the planthopper Sogatella furcifera (Horváth) in a persistent, circular, and propagative manner. Researchers currently lack suitable methods for assaying the activity of SRBSDV in vitro and preserving the virus all year. We used a microinjection method to directly inject SRBSDV extracts into the hemocoel of S. furcifera nymphs. SRBSDV was subsequently detected by Reverse Transcription-Polymerase Chain Reaction in more than 56.7% of the insects after 5 d and 60% of healthy rice plants fed by these insects also became SRBSDV infected. Moreover, injecting planthopper with an extract of SRBSDV-infected rice plant that had been frozen at -80°C for 220 d caused 63.3% to become viruliferous. These results indicate that SRBSDV can be successfully transmitted to S. furcifera by microinjection, and that extracts of SRBSDV-infected rice plants frozen at -80°C for 220 d still contain sufficient active SRBSDV to infect S. furcifera. We provide a novel way to preserve SRBSDV all year by injecting S. furcifera with the SRBSDV extract.