Laodelphax Striatellus Research Articles

Field spray abdominal gland secretions of rove beetles: Effects on the pest abundance and arthropod community

AbstractAlternative environmentally friendly methods for pest control are in high demand because of the environmental impacts of pesticides. Notably, predator‐released kairomone is a natural compound released by natural enemies, which mediates non‐consumptive effects between natural enemies and prey. However, this novel pest control agent is underutilized relative to pesticides and natural enemies. Additionally, the effects of spraying predator kairomone on the number and diversity of arthropods in fields and whether this method is environmental‐friendly are poorly understood. In the present study, a predator kairomone, rove beetle (Paederus fuscipes Curtis) abdominal gland secretion (AGS), was sprayed in rice fields to investigate whether AGS can suppress pest populations or will affect the fields’ arthropod communities. After AGS spraying, the abundance of arthropods decreased throughout the first 12‐d period, including arthropod pests such as hemipterans (small brown planthopper, Laodelphax striatellus (Fallén), brown planthopper, Nilaparvata lugens (Stål), white‐backed planthopper, Sogatella furcifera (Horváth), and leafhoppers), and lepidopterans (rice leaf folder, Cnaphalocrocis medinalis Guenée). The abundance of arthropod predators was not affected, except for predatory spiders, which decreased, and rove beetles (P. fuscipes), which increased. In the terms of arthropod diversity, neither pests nor their natural enemies were changed by AGS application. This work highlights that predator kairomone can temporarily suppress pest populations in fields but has no adverse effects on arthropod diversity; thus, this approach is environmentally friendly and can be used in real‐world applications. Broadly, present studies suggest that the application of predator kairomone may have synergistic or cumulative effects on pest suppression.

Investigation of the Association between the Energy Metabolism of the Insect Vector Laodelphax striatellus and Rice Stripe Virus (RSV).

Viruses, as intracellular parasites, rely on the host organism to complete their life cycle. Although over 70% of plant viruses are transmitted by insect vectors, the role of vector energy metabolism on the infection process of insect-borne plant viruses is unclear. In this study, full-length cDNAs of three energy metabolism-related genes (LsATPase, LsMIT13 and LsNADP-ME) were obtained from the small brown planthopper (SBPH, Laodelphax striatellus), which transmits the Rice stripe virus (RSV). Expression levels of LsATPase, LsMIT13 and LsNADP-ME increased by 105%, 1120% and 259%, respectively, due to RSV infection. The repression of LsATPase, LsMIT13 or LsNADP-ME by RNAi had no effect on RSV nucleocapsid protein (NP) transcripts or protein levels. The repression of LsATPase caused a significant increase in LsMIT13 and LsNADP-ME transcript levels by 230% and 217%, respectively, and the repression of LsMIT13 caused a significant increase in LsNADP-ME mRNA levels. These results suggested that the silencing of LsATPase induced compensatory upregulation of LsMIT13 and LsNADP-ME, and silencing LsMIT13 induced compensatory upregulation of LsNADP-ME. Further study indicated that the co-silencing of LsATPase, LsMIT13 and LsNADP-ME in viruliferous SBPHs increased ATP production and RSV loads by 182% and 117%, respectively, as compared with nonviruliferous SBPHs. These findings indicate that SBPH energy metabolism is involved in RSV infection and provide insight into the association between plant viruses and energy metabolism in the insect vector.

Transcriptome analysis reveals different response of resistant and susceptible rice varieties to rice stripe virus infection

Rice stripe disease, caused by rice stripe virus (RSV) which is transmitted by small brown planthopper (SBPH, Laodelphax striatellus Fallen), resulted in serious losses to rice production during the last 2 decades. Research on the molecular differences between resistant and susceptible rice varieties and the interaction between rice and RSV remains inadequate. In this study, RNA-Seq was used to analyze the transcriptomic differences between the resistant and susceptible rice varieties at different times post RSV infection. Through Gene Ontology (GO) annotation, the differentially expressed genes (DEGs) related to transcription factors, peroxidases, and kinases of 2 varieties at 3 time points were identified. Comparing these 2 varieties, the DEGs associated with these 3 GOs were numerically less in the resistant variety than in the susceptible variety, but the expression showed a significant up- or down-regulation trend under the conditions of |log2(Fold change)|>0 &Padj<0.05 by significance analysis. Then through Kyoto Encyclopedia of Genes and Genomes (KEGG) annotation, DEGs involved in some pathways that have a contribution to disease resistance including plant hormone signal transduction and plant–pathogen interaction were found. The results showed that resistance responses regulated by abscisic acid (ABA) and brassinosteroids (BR) were the same for 2 varieties, but that mediated by salicylic acid (SA) and jasmonic acid (JA)/ethylene (ET) were different. The DEGs in resistant and susceptible varieties at the 3 time points were identified in both PAMP-triggered immunity (PTI) and Effector protein-triggered immunity (ETI), with that most of the unigenes of the susceptible variety were involved in PTI, whereas most of the unigenes of the resistant variety were involved in ETI. These results revealed the different responses of resistant and susceptible varieties in the transcription level to RSV infection.

Activating pathway of three metabolic detoxification phases via down-regulated endogenous microRNAs, modulates triflumezopyrim tolerance in the small brown planthopper, Laodelphax striatellus (Fallén)

Frequent use of insecticide causes an environmental hazard, and also leads pest to develop insecticide resistance. Enhancement of metabolic detoxification and reduction of target sensitivity are the primary mechanism of insecticide resistance. Clarifying the regulatory pathway of resistance mechanism states a pivotal theoretical foundation of delaying insecticide resistance development. Here, we show that three endogenous microRNAs, PC-3p-2522_840, PC-3p-446_6601 and PC-5p-3096_674, are required for the small brown planthopper (SBPH) to modulate triflumezopyrim tolerance via activating pathways of three metabolic detoxification phases. Twenty-one down-regulated miRNAs were acquired, and PC-5p-3096_674, PC-3p-446_6601 and PC-3p-2522_840 were the three most significantly down-regulated miRNAs during triflumezopyrim exposure. The mortality of SBPH was significantly increased after over-supplementation of PC-5p-3096_674, PC-3p-446_6601 and PC-3p-2522_840, with triflumezopyrim exposure. Moreover, the interactions between PC-3p-2522_840 and cytochrome P450 CYP6FL1, PC-3p-446_6601 and glutathione S-transferase GSTD2, UDP-Glycosyltransferase UGT386F1, PC-5p-3096_674 and ATP-binding cassette transporters ABCA3 were systematically demonstrated through the dual luciferase reporter assay. Besides, the mortality of SBPH was significantly increased after knockdown of CYP6FL1, GSTD2, UGT386F1 and ABCA3 with triflumezopyrim exposure. These findings uncover a strategy whereby the SBPH weakens three endogenous microRNAs to activate pathways of three metabolic detoxification phases via targeting CYP6FL1, GSTD2, UGT386F1 and ABCA3 and promotes its tolerance to triflumezopyrim.

Genome-Wide Identification and Expression Profiling of the Wnt Gene Family in Three Rice Planthoppers: Sogatella furcifera, Laodelphax striatellus, and Nilaparvata lugens.

The Wnt gene family plays essential roles in regulating many developmental processes, including the maintenance of stem cells, cell division, and cell migration. The number of Wnt genes varies among species. Due to the diversity and importance of their functions, the Wnt gene family has gained extensive research interest in various animal species from invertebrates to vertebrates. However, knowledge of the Wnt gene family is limited in rice planthoppers. Three planthopper species, the white-backed planthopper (Sogatella furcifera Horvath), the small brown planthopper (Laodelphax striatellus Fallén) and the brown planthopper (Nilaparvata lugens Stål) (Hemiptera: Delphacidae), are devastating specialist pests of rice and cause serious damage to rice plants. To better study the evolution and function of the Wnt gene family in rice planthoppers, we identified 8 Wnt family genes in three rice planthoppers with both genomic and extensive transcriptomic resources available. We conducted a systematic analysis of the three kinds of rice planthoppers and analyzed the dynamic patterns of gene conservation, as well as Wnt gene loss and duplication. The expression profiles in different developmental stages of S. furcifera and different adult organs and tissues of L. striatellus provide preliminary functional implications for the Wnt genes in rice planthopper. This study presents the first genome-wide study of the Wnt gene family in rice planthoppers, and our findings provide insights into Wnt function and evolution in rice planthoppers.

Sensitivity Differences and Biochemical Characteristics of Laodelphax striatellus (Fallén) to Seven Insecticides in Different Areas of Shandong, China

Simple SummaryThe sensitivity detection of pests to insecticides is useful to the strategies of integrated pest management (IPM) in the field. The sensitivities of six Laodelphax striatellus Fallén populations from different areas in Shandong, China to seven insecticides acting on the nicotinic acetylcholine receptor (nAChR) were investigated. The biochemical characteristics of different populations were also studied. The results showed that all the field populations are sensitive to clothianidin, nitenpyram, and triflumezopyrim, but some field populations have developed resistance to other insecticides. The populations showed different metabolic enzyme contents caused by the expression of related genes, and no known mutations in the target gene nAChR β1 subunit were found in any of the populations. These results provide valuable information for the management strategies of L. striatellus in field.Laodelphax striatellus Fallén is one of the main pests that can severely harm rice, corn, and wheat. Insecticides acting on the nicotinic acetylcholine receptor (nAChR) are the main type of pesticides used for the control of L. striatellus in Shandong Province, a major grain-producing region in China. In this study, the rice seedling dipping method was used to determine the sensitivities of six field L. striatellus populations in Shandong to seven insecticides acting on nAChR. The results showed that all the field populations were sensitive to clothianidin, nitenpyram, and triflumezopyrim, and the Jiaxiang population exhibited the lowest resistance ratio (RR) to imidacloprid, dinotefuran, sulfoxaflor, and thiamethoxam. The Donggang population showed a medium-level resistance to imidacloprid, with the highest RR of 17.48-fold. The Yutai population showed low-level resistance to imidacloprid and thiamethoxam, with RRs of 7.23- and 7.02-fold, respectively. The contents of cytochrome P450 monooxygenase (P450s), carboxylesterase (CarE), and glutathione S-transferase (GST) were the highest in the Donggang population and the lowest in the Jiaxiang population. The P450 gene CYP314A1 and the CarE gene LsCarE12 were highly up-regulated in all populations. No mutations of V62I, R81T, and K265E in the nAChR β1 subunit were found in any of the populations. These results provide valuable information for the strategies of resistance management of L. striatellus in the field.

Study about photoinduction-based technology for trapping small brown planthopper

To provide a theory to guide the selection of the illumination parameters of light emitting diode (LED)-based light sources used for trapping Laodelphax striatellus, we used LED light sources and devices built in-house to detect L. striatellus phototactic behavior. Through phototaxis screening experiments of different light sources and the comparative experimental method, we analyzed the response patterns of L. striatellus to wavelength, light intensity, layout, flash frequency of monochromatic light sources, as well as combined color light sources, and discussed the mechanisms of the phototactic behavior of L. striatellus under different light sources. The results of the monochromatic light experiment showed that the trapping rate of the L. striatellus to the linear blue light source of 460 nm was the highest and was also significantly affected by the light intensity. The results of the experiments with the combined color light sources showed that compared with the linear 460 nm blue light source, the trapping rate of the L. striatellus was significantly improved by the polychromatic light, and the blue–green light led to the best improvement, reaching 1.5 times that of the trapping rate in the case of monochromatic light sources. The wavelength composition, light intensity, shape, and flash frequency of the light source used in this study can provide a theoretical basis for the development of LED-based light traps specifically for L. striatellus.

The Homeodomain-Leucine Zipper Genes Family Regulates the Jinggangmycin Mediated Immune Response of Oryza sativa to Nilaparvata lugens, and Laodelphax striatellus

The homeodomain-leucine zipper (HDZIP) is an important transcription factor family, instrumental not only in growth but in finetuning plant responses to environmental adversaries. Despite the plethora of literature available, the role of HDZIP genes under chewing and sucking insects remains elusive. Herein, we identified 40 OsHDZIP genes from the rice genome database. The evolutionary relationship, gene structure, conserved motifs, and chemical properties highlight the key aspects of OsHDZIP genes in rice. The OsHDZIP family is divided into a further four subfamilies (i.e., HDZIP I, HDZIP II, HDZIP III, and HDZIP IV). Moreover, the protein–protein interaction and Gene Ontology (GO) analysis showed that OsHDZIP genes regulate plant growth and response to various environmental stimuli. Various microRNA (miRNA) families targeted HDZIP III subfamily genes. The microarray data analysis showed that OsHDZIP was expressed in almost all tested tissues. Additionally, the differential expression patterns of the OsHDZIP genes were found under salinity stress and hormonal treatments, whereas under brown planthopper (BPH), striped stem borer (SSB), and rice leaf folder (RLF), only OsHDZIP3, OsHDZIP4, OsHDZIP40, OsHDZIP10, and OsHDZIP20 displayed expression. The qRT-PCR analysis further validated the expression of OsHDZIP20, OsHDZIP40, and OsHDZIP10 under BPH, small brown planthopper (SBPH) infestations, and jinggangmycin (JGM) spraying applications. Our results provide detailed knowledge of the OsHDZIP gene family resistance in rice plants and will facilitate the development of stress-resilient cultivars, particularly against chewing and sucking insect pests.

The crystal structure of Cry78Aa from Bacillus thuringiensis provides insights into its insecticidal activity

Genetically modified plants with insecticidal proteins from Bacillus thuringiensis (Bt) have been successfully utilized to control various kinds of pests in crop production and reduce the abuse of pesticides. However, a limited number of genes are available for the protection of crops from rice planthopper. Recently, Cry78Aa protein from Bt strain C9F1 has been found to have high insecticidal activity against Laodelphax striatellus and Nilaparvata lugens. It is the first reported single-component protein in the world to combat rice planthoppers, making it very promising for use in transgenic crops. The ambiguous mechanism of Cry78Aa functions prevented further engineering or application. Here, we report the crystal structure of Cry78Aa, which consists of two domains: a C-terminal β-pore forming domain belonging to the aerolysin family and an N-terminal trefoil domain resembling the S-type ricin B lectin. Thus, Cry78Aa could represent a distinctive type of β-pore forming toxin. We also found that Cry78Aa binds carbohydrates such as galactose derivatives and is essential for insecticidal activity against Laodelphax striatellus. Our results suggest a mechanism underlying the function of Cry78Aa against rice planthoppers and pave the way to maximizing the usage of the toxin.

Diversity of leaf hoppers on fruit crops and weeds in North Kashmir

This study analyses the diversity of leafhopper fauna at six locations (Wadura, Arampora, Dangiwacha, Imberzalwari from District Baramulla and Chogul and Chetkak from District Kupwara) occurring on various fruit crops and weeds. Diversity indices such as species diversity index, evenness index, richness index and abundance were computed. These reveal that six species infest these, of which those infesting fruit trees include Empoasca decipiens, Empoasca fabae, Agallia spp., Aconeurella erebrus and Exitianus indicus; and Stirellus spp., Maiestas dorsalis, Macrosteles quadrilineatus, Exitianus indicus and one plant hopper species viz., Laodelphax striatellus infest weeds. Maximum abundance was observed to be of A. decedens on fruit trees and Stirellus spp. on the weed flora.

Threonyl-tRNA synthetase gene, a potential target for RNAi-based control of three rice planthoppers.

RNA interference (RNAi) has potential as a new strategy for pest control. However, the current overemphasis on the control of a single pest increased control costs. The aim of this study was to find a green method of controlling several pests without affecting the natural enemies with a single target gene. One possible RNAi target is the threonyl-tRNA synthetase (ThrRS), which is conserved and plays a significant role in protein biosynthesis. In this study, one threonyl-tRNA synthetase gene (NlthrS) was identified from the brown planthopper (Nilaparvata lugens). Spatio-temporal expression pattern analysis showed that NlthrS was highly expressed in the ovary, late embryogenesis, nymphs and female adults. In addition, RNAi-mediated knockdown of NlthrS caused 85.6% nymph mortality, 100% female infertility, molting disorder, extended nymph duration and shortened adult longevity. Target-specific results were obtained when dsNlthrS was used to interfere with the whiteback planthopper (Sogatella furcifera), small brown planthopper (Laodelphax striatellus), zig-zag winged leafhopper (Inazuma dorsalis) and their natural enemy (green mirid bug, Cyrtorhinus lividipennis). In addition, dsNlthrS could cause high mortalities of three species of planthoppers (85.6-100%), while only dsNlthrS-1 led to the death (97.3%) of I. dorsalis that was not affected by dsNlthrS-2. Furthermore, neither dsNlthrS-1 nor dsNlthrS-2 could influence the survival of C. lividipennis. The results reveal the biological functions of ThrRS in N. lugens in addtion toits protein synthesis, deepening our understanding of tRNA synthase in insects and providing a new method for the control of several rice pests via one dsRNA design. © 2022 Society of Chemical Industry.

Laodelphax striatellus saliva mucin enables the formation of stylet sheathes to facilitate its feeding and rice stripe virus transmission.

Laodelphax striatellus transmits rice stripe virus (RSV) during sap feeding on the rice plant. The insect saliva proteins have direct and indirect roles in mediating RSV transmission; however, the function of most saliva proteins remains unclear. In this study, we sequenced L. striatellus saliva proteins using shotgun liquid chromatography-electrospray ionization-tandem mass spectrometry. We identified 41 secreted saliva proteins, among which a saliva mucin-like protein, designated LssaMP, was the most abundant. In silico analysis revealed the sequence conservation among planthoppers. We revealed that the LssaMP gene is specifically expressed in the salivary glands and the protein is secreted as a component of gel saliva. Using LssaMP-specific double-stranded RNA (dsRNA) to silence gene expression, we revealed that LssaMP is required for formation of the salivary sheath, an important structure for sap feeding. Disrupting LssaMP expression resulted in inefficient formation of the feeding structure, thereby stopping insects from secreting watery saliva and acquiring sufficient nutrients from the phloem sap. We confirmed that RSV is mainly released via the watery saliva, which passes through the salivary sheathes into the plant phloem. An insufficient feeding structure results in decreased release of watery saliva, as well as the arboviruses. This study clarified the function of an insect saliva protein in mediating insect feeding, as well as arbovirus transmission. © 2022 Society of Chemical Industry.

PHYTOPHAGES IN THE AGROCENOSIS OF SPRING WHEAT IN THE PAVLODAR REGION

To prevent losses of wheat yield from pests, it is necessary to update information on the patterns of formation of the phytosanitary situation in agrobiocenoses, according to which protective measures are planned and organized. In order to assess the phytosanitary situation of spring wheat crops, studies were carried out in the Pavlodar region, as one of the main regions of the republic for the production of grain of this crop. The paper reflects monitoring data on the phytophages population of spring wheat crops in the main grain-sowing areas of the Pavlodar region. The species composition of cereal crop pests that have a direct effect on productivity, qualitative and quantitative indicators of agricultural crops has been established. The obtained results showed that starting from the germination and up to the stem elongation phase, cereal crops were colonized by latent-stem pests and Phyllotreta vittula. Haplothrips tritici, Psammotettix striatus and Trigonotylus ruficornis dominated in the stem elongation and heading phases. Schizaphis graminum, Haplothrips tritici in two forms (larvae and adults) and Laodelphax striatella dominated in the phase of grain formation-filling and milk development phase. The study showed that during the initial phases of wheat development, the majority of pests develop and feed on wild weed plants, subsequently migrating to the cereals.

Comprehensive Bioinformatics and Expression Analysis of the TLP Gene Family Revealed Its Role in Regulating the Response of Oryza sativa to Nilaparvata lugens, Laodelphax striatellus, and Jinggangmycin

Thaumatin-like proteins (TLPs), which belong to pathogenesis-related (PR) protein family 5 (PR5), are involved in the plant host defense and developmental processes. Detailed information regarding the TLP gene family in rice remains elusive. Here, we identified 43 OsTLP genes from the rice genome database. The in silico analysis comprised of the evolutionary tree, gene structure, conserved motifs, and chemical properties highlighted the key aspects of the OsTLP genes. By phylogenetic analysis, the OsTLP genes were classified into ten groups (OsTLPI-OsTLPX). Gene ontology (GO) analysis showed that OsTLP genes regulate plant growth and response to various environmental stimuli. Moreover, most of the OsTLP genes are expressed in almost all tissues. Microarray data showed differential expression trends of OsTLP genes under salinity stress and hormonal treatments, whereas under BPH, SSB, and RFL, only OsTLP1, OsTLP2 and OsTLP27 were expressed. The qRT-PCR analysis showed OsTLP27 as the prominent gene, displayed by its upregulated expression under JGM. Our results provide detailed knowledge of OsTLP gene resistance in rice plants, and we believe the current study will facilitate the development of cultivars resistant to biotic/abiotic stress, particularly stress caused by the chewing and sucking of insect pests.

Structural insights into the interaction between gabazine (SR-95531) and Laodelphax striatellus GABA receptors.

γ-Aminobutyric acid receptors (GABARs) mediate fast inhibitory neurotransmission and are targets for insecticides. GABARs are composed of five subunits, the composition of which dictates the pharmacological characteristics of GABARs. Both competitive and noncompetitive GABAR antagonists can be used as insecticides. Gabazine is a potent competitive antagonist of mammalian α1β2γ2 GABARs; however, it is less potent against insect GABARs. To explore how gabazine interacts with GABARs, we examined whether the sensitivity of the small brown planthopper (Laodelphax striatellus) RDL GABAR (LsRDLR) to gabazine is increased when its amino acid residues are substituted with α1β2γ2 GABAR residues. In the results, two of the generated mutants showed enhanced gabazine sensitivity. Docking simulations of gabazine using LsRDLR homology models and an α1β2γ2 GABAR cryo-EM structure revealed that the accommodation of gabazine into the “aromatic box” in the orthosteric site lowered the binding energy. This information may help in designing GABAR-targeting insecticides with novel modes of action.

Species identification of bacterial communities in the small brown planthopper, Laodelphax striatellus (Hemiptera: Delphacidae)

AbstractMicrobes are prevalent and abundant in diverse insects. Many microbes are known to influence host fitness. The small brown planthoppers Laodelphax striatellus Fallen is a notorious plant sap‐feeding pest causing heavy loss to rice yield. Some L. striatellus‐associated microbes have been surveyed partially. However, their microbial communities at the species level were poorly identified. In this study, we investigated the bacterial community from 7 populations of L. striatellus using the restriction fragment length polymorphism (RFLP)‐PCR of the 16S rRNA gene. The identified bacteria were assigned into 8 species, the top three of which (Wolbachia sp., Pseudomonas poae and Asaia sp.) accounted for 96% of amplified bacterial sequences. The Wolbachia is of supergroup B and the most abundant in all wild populations. In addition, P. poae was reported in L. striatellus and showed mild pathogenicity. Altogether, our results provide detailed information on the bacterial community in L. striatellus. More research is required to explore the effects of symbiotic bacteria on the fitness of small brown planthoppers.

MAPKs trigger antiviral immunity by directly phosphorylating a rhabdovirus nucleoprotein in plants and insect vectors.

Signaling by the evolutionarily conserved mitogen-activated protein kinase or extracellular signal-regulated kinase (MAPK/ERK) plays critical roles in converting extracellular stimuli into immune responses. However, whether MAPK/ERK signaling induces virus immunity by directly phosphorylating viral effectors remains largely unknown. Barley yellow striate mosaic virus (BYSMV) is an economically important plant cytorhabdovirus that is transmitted by the small brown planthopper (SBPH, Laodelphax striatellus) in a propagative manner. Here, we found that the barley (Hordeum vulgare) MAPK MPK3 (HvMPK3) and the planthopper ERK (LsERK) proteins interact with the BYSMV nucleoprotein (N) and directly phosphorylate N protein primarily on serine 290. The overexpression of HvMPK3 inhibited BYSMV infection, whereas barley plants treated with the MAPK pathway inhibitor U0126 displayed greater susceptibility to BYSMV. Moreover, knockdown of LsERK promoted virus infection in SBPHs. A phosphomimetic mutant of the N Ser290 (S290D) completely abolished virus infection because of impaired self-interaction of BYSMV N and formation of unstable N-RNA complexes. Altogether, our results demonstrate that the conserved MAPK and ERK directly phosphorylate the viral nucleoprotein to trigger immunity against cross-kingdom infection of BYSMV in host plants and its insect vectors.

Silencing suppressors of rice black-streaked dwarf virus and rice stripe virus hijack the 26S proteasome of Laodelphax striatellus to facilitate virus accumulation and transmission.

Rice black-streaked dwarf virus (RBSDV) is transmitted by small brown planthopper (Laodelphax striatellus [L. striatellus]) and causes devastating disease in rice. P9-1 has silencing suppression activity and is the key protein for viroplasm formation in RBSDV-infected plants and insects; however, its exact function is poorly understood. In this study, the P9-1 of RBSDV interacted with L. striatellus 26S proteasome subunit RPN8. RBSDV accumulation in L. striatellus increased after the 26S proteasome was disrupted by silencing the RPN8 expression. This finding indicated that L. striatellus 26S proteasome played a defense role against RBSDV infection by regulating RBSDV accumulation. Further investigations revealed that P9-1 could competitively bind to RPN8 with RPN7, thereby disrupting the assembly of 26S proteasome in L. striatellus and promoting the infection of RBSDV in insect vectors, and further affecting the transmission of the virus to rice by insect vectors. Similar to P9-1, rice stripe virus (RSV) NS2, a weak silencing suppressor, regulated virus accumulation and transmission by hijacking RPN8 to interfere with the function of 26S proteasome in L. striatellus. These results suggest that viruses promote their own infection via interfering with ubiquitination pathway of insect vectors, and this mechanism might be of universal importance. These findings provide a new insight into the mechanism of virus transmission in insect vectors. © 2022 Society of Chemical Industry.

The Function of Nilaparvata lugens (Hemiptera: Delphacidae) E74 and Its Interaction With βFtz-F1

Drosophila E74 is an early gene located in the polytene chromosome 74EF puff position. E74 controls the production of late genes, indicating that it plays a crucial role in this cascade model. Nilaparvata lugens E74 is closely related to Diaphorina citri, Bemisia tabaci, and Laodelphax striatellus. After downregulating E74, molting, and nymphal mortality were increased, and ovarian development was delayed. Moreover, the expression of Vg was reduced at the transcriptional level, as measured by qRT-PCR, and the content of Vg protein was reduced, as detected by Western blotting. After downregulating E74, the expression of hormone-related genes, including Tai, βFtz-F1, Met, Kr-h1, UspA, UspB, E93, and Br, was changed. The expression of E74 was significantly decreased after downregulating hormone-related genes. When the expression of E74 and βFtz-F1 was downregulated together, nymph mortality and molting mortality were higher than those when E74 or βFtz-F1 was downregulated alone. Thus, E74 probably interacts with βFtz-F1 at the genetic level. In summary, this study showed that E74 plays a crucial role in the development, metamorphosis and reproduction of N. lugens, possibly via the interaction with βFtz-F1 at the genetic level. This study provides a basis for the development of new target-based pesticides and new methods for the effective control of N. lugens.

Genetic evidence of transoceanic migration of the small brown planthopper between China and Japan.

The small brown planthopper, Laodelphax striatellus (Fallén), is an important pest of rice. It is suspected of migrating over the sea from China to Japan. However, where in China it comes from and how it affects Japanese populations remain unclear. Here, we studied the genetic structure of 15 L. striatellus populations sampled from Japan and China using single nucleotide polymorphisms generated by the double digest restriction site-associated DNA sequencing technique. We found weak genetic differentiation between the Chinese and Japanese populations. Our data revealed migration signals of L. striatellus from China to southern and northern Japan. However, the source regions of the immigrants remain unclear due to the low genetic differentiation between populations. Our results also pointed to the possibility of backward gene flow from Japanese to Chinese populations. We suspect that the south-eastern wind associated with the East Asian summer monsoon may facilitate the reverse migration of L. striatellus from Japan to China. Interestingly, we found that the X chromosome displayed relatively higher genetic differentiation among populations and suffered more intensive selection pressure than autosomes. We provide genetic evidence of transoceanic migration of L. striatellus from China to Japan and found that the X chromosome can aid the deciphering of the migration trajectories of species with low genetic differentiation. These findings have implications for forecasting the outbreak of this pest and also provide insights into how to improve the tracking of the migration routes of small insects via population genomics. © 2022 Society of Chemical Industry.