Cross-kingdom RNA interference mediated by insect salivary microRNAs may suppress plant immunity.

Communication between insects and plants relies on the exchange of bioactive molecules that traverse the species interface. Although proteinic effectors have been extensively studied, our knowledge of other molecules involved in this process remains limited. In this study, we investigate the role of salivary microRNAs (miRNAs) from the rice planthopper Nilaparvata lugens in suppressing plant immunity. A total of three miRNAs were confirmed to be secreted into host plants during insect feeding. Notably, the sequence-conserved miR-7-5P is specifically expressed in the salivary glands of N. lugens and is secreted into saliva, distinguishing it significantly from homologues found in other insects. Silencing miR-7-5P negatively affects N. lugens feeding on rice plants, but not on artificial diets. The impaired feeding performance of miR-7-5P-silenced insects can be rescued by transgenic plants overexpressing miR-7-5P. Through target prediction and experimental testing, we demonstrate that miR-7-5P targets multiple plant genes, including the immune-associated bZIP transcription factor 43 (OsbZIP43). Infestation of rice plants by miR-7-5P-silenced insects leads to the increased expression of OsbZIP43, while the presence of miR-7-5P counteracts this upregulation effect. Furthermore, overexpressing OsbZIP43 confers plant resistance against insects which can be subverted by miR-7-5P. Our findings suggest a mechanism by which herbivorous insects have evolved salivary miRNAs to suppress plant immunity, expanding our understanding of cross-kingdom RNA interference between interacting organisms.

The JAK-STAT pathway promotes persistent viral infection by activating apoptosis in insect vectors.

The Janus kinase-signal transducer and activator of transcription (JAK-STAT) pathway is an evolutionarily conserved signaling pathway that can regulate various biological processes. However, the role of JAK-STAT pathway in the persistent viral infection in insect vectors has rarely been investigated. Here, using a system that comprised two different plant viruses, Rice stripe virus (RSV) and Rice black-streaked dwarf virus (RBSDV), as well as their insect vector small brown planthopper, we elucidated the regulatory mechanism of JAK-STAT pathway in persistent viral infection. Both RSV and RBSDV infection activated the JAK-STAT pathway and promoted the accumulation of suppressor of cytokine signaling 5 (SOCS5), an E3 ubiquitin ligase regulated by the transcription factor STAT5B. Interestingly, the virus-induced SOCS5 directly interacted with the anti-apoptotic B-cell lymphoma-2 (BCL2) to accelerate the BCL2 degradation through the 26S proteasome pathway. As a result, the activation of apoptosis facilitated persistent viral infection in their vector. Furthermore, STAT5B activation promoted virus amplification, whereas STAT5B suppression inhibited apoptosis and reduced virus accumulation. In summary, our results reveal that virus-induced JAK-STAT pathway regulates apoptosis to promote viral infection, and uncover a new regulatory mechanism of the JAK-STAT pathway in the persistent plant virus transmission by arthropod vectors.

Comparative transcriptomic analysis of salivary glands between the zoophytophagous Cyrtorhinus lividipennis and the phytozoophagous Apolygus lucorum.

BACKGROUND: Saliva plays a crucial role in shaping the feeding behavior of insects, involving processes such as food digestion and the regulation of interactions between insects and their hosts. Cyrtorhinus lividipennis serves as a predominant natural enemy of rice pests, while Apolygus lucorum, exhibiting phytozoophagous feeding behavior, is a destructive agricultural pest. In this study, a comparative transcriptome analysis, incorporating the published genomes of C.lividipennis and A.lucorum, was conducted to reveal the role of salivary secretion in host adaptation. RESULTS: In contrast to A.lucorum, C.lividipennis is a zoophytophagous insect. A de novo genome analysis of C.lividipennis yielded 19,706 unigenes, including 16,217 annotated ones. On the other hand, A.lucorum had altogether 20,111 annotated genes, as obtained from the published official gene set (20,353 unigenes). Functional analysis of the top 1,000 salivary gland (SG)-abundant genes in both insects revealed that the SG was a dynamically active tissue engaged in protein synthesis and secretion. Predictions of other tissues and signal peptides were compared. As a result, 94 and 157 salivary proteins were identified in C.lividipennis and A.lucorum, respectively, and were categorized into 68 and 81 orthogroups. Among them, 26 orthogroups were shared, potentially playing common roles in digestion and detoxification, including several venom serine proteases. Furthermore, 42 and 55 orthogroups were exclusive in C.lividipennis and A.lucorum, respectively, which were exemplified by a hyaluronidase in C.lividipennis that was associated with predation, while polygalacturonases in A.lucorum were involved in mesophyll-feeding patterns. CONCLUSIONS: Findings in this study provide a comprehensive insight into saliva secretions in C.lividipennis and A.lucorum via a transcriptome approach, reflecting the intricate connections between saliva secretions and feeding behaviors. It is found that conserved salivary secretions are involved in shaping the overlapping feeding patterns, while a plethora of unique salivary secretions may drive the evolution of specific feeding behaviors crucial for their survival. These results enhance our understanding of the feeding mechanisms in different insects from the perspective of saliva and contribute to future environmentally friendly pest control by utilizing predatory insects.

Horizontally Transferred Salivary Protein Promotes Insect Feeding by Suppressing Ferredoxin-Mediated Plant Defenses.

Herbivorous insects such as whiteflies, planthoppers, and aphids secrete abundant orphan proteins to facilitate feeding. Yet, how these genes are recruited and evolve to mediate plant-insect interaction remains unknown. In this study, we report a horizontal gene transfer (HGT) event from fungi to an ancestor of Aleyrodidae insects approximately 42 to 190 million years ago. BtFTSP1 is a salivary protein that is secreted into host plants during Bemisia tabaci feeding. It targets a defensive ferredoxin 1 in Nicotiana tabacum (NtFD1) and disrupts the NtFD1-NtFD1 interaction in plant cytosol, leading to the degradation of NtFD1 in a ubiquitin-dependent manner. Silencing BtFTSP1 has negative effects on B. tabaci feeding while overexpressing BtFTSP1 in N. tabacum benefits insects and rescues the adverse effect caused by NtFD1 overexpression. The association between BtFTSP1 and NtFD1 is newly evolved after HGT, with the homologous FTSP in its fungal donor failing to interact and destabilize NtFD1. Our study illustrates the important roles of horizontally transferred genes in plant-insect interactions and suggests the potential origin of orphan salivary genes.

Long-wave opsin involved in body color plastic development in Nilaparvata lugens.

BACKGROUND: As one of the components of visual photopigments in photoreceptor cells, opsin exhibits different spectral peaks and plays crucial roles in visual function. Besides, it is discovered to evolve other functions despite color vision. However, research on its unconventional function is limited nowadays. With the increase in genome database numbers, various numbers and types of opsins have been identified in insects due to gene duplications or losses. The Nilaparvata lugens (Hemiptera) is a rice pest known for its long-distance migration capability. In this study, opsins were identified in N. lugens and characterized by genome and transcriptome analyses. Meanwhile, RNA interference (RNAi) was carried out to investigate the functions of opsins, and then the Illumina Novaseq 6000 platform-based transcriptome sequencing was performed to reveal gene expression patterns. RESULTS: Four opsins belonging to G protein-coupled receptors were identified in the N. lugens genome, including one long-sensitive opsin (Nllw) together with two ultraviolet-sensitive opsins (NlUV1/2) and an additional new opsin with hypothesized UV peak sensitivity (NlUV3-like). A tandem array of NlUV1/2 on the chromosome suggested the presence of a gene duplication event, with similar exons distribution. Moreover, as revealed by spatiotemporal expression, the four opsins were highly expressed in eyes with age-different expression levels. Besides, RNAi targeting each of the four opsins did not significantly affect the survival of N. lugens in phytotron, but the silencing of Nllw resulted in the melanization of body color. Further transcriptome analysis revealed that silencing of Nllw resulted in up-regulation of a tyrosine hydroxylase gene (NlTH) and down-regulation of an arylalkylamine-N-acetyltransferases gene (NlaaNAT) in N. lugens, demonstrating that Nllw is involved in body color plastic development via the tyrosine-mediated melanism pathway. CONCLUSIONS: This study provides the first evidence in a Hemipteran insect that an opsin (Nllw) takes part in the regulation of cuticle melanization, confirming a cross-talk between the gene pathways underlying the visual system and the morphological differentiation in insects.

Complete genome analysis of a novel chuvirus from a southern green stink bug (Nezara viridula).

A novel chuvirus from a southern green stink bug (Nezara viridula) was identified by RNA sequencing in this study and was tentatively named "Ningbo southern green stink bug chuvirus 1" (NBSGSBV-1). The complete genome sequence of NBSGSBV-1 consists of 11,375 nucleotides, and the genome was found to be circular by 'around-the-genome' reverse transcription polymerase chain reaction (RT-PCR) and Sanger sequencing. Three open reading frames (ORFs) were predicted in the NBSGSBV-1 genome, encoding a large polymerase protein (L protein), a glycoprotein (G protein), and a nucleocapsid protein (N protein). A phylogenetic tree was constructed based on all of the currently available RNA-dependent RNA polymerase amino acid sequences of viruses of the family Chuviridae, and NBSGSBV-1 was found to cluster together with Sanya chuvirus 2 and Hubei odonate virus 11, indicating that NBSGSBV-1 might belong to the genus Odonatavirus. Five conserved sites were identified in the L proteins of NBSGSBV-1 and other chuviruses. The abundance and characteristics of the NBSGSBV-1-derived small interfering RNAs suggested that NBSGSBV-1 actively replicates in the host insect. To the best of our knowledge, this is the first report of a chuvirus identified in a member of the insect family Pentatomidae. The discovery and characterization of NBSGSBV-1 will help us to understand the diversity of chuviruses in insects.

A comprehensive omics analysis and functional survey of cuticular proteins in the brown planthopper.

Cuticle, mainly composed of chitin and cuticular proteins (CPs), is a multifunctional structure of arthropods. CPs usually account for >1% of the total insect proteins. Why does an insect encode so many different CP genes in the genome? In this study, we use comprehensive large-scale technologies to study the full complement of CPs (i.e., the CP-ome) of the brown planthopper (BPH), Nilaparvata lugens, a major rice plant pest. Eight CP families (CPR, CPF, TWDL, CPLCP, CPG, CPAP1, CPAP3, and CPAPn) including 140 proteins in BPH, in which CPAPn is a CP family that we discovered. The CPG family that was considered to be restricted to the Lepidoptera has also been identified in BPH. As reported here, CPLCP family members are characterized by three conserved sequence motifs. In addition, we identified a testis protein family with a peritrophin A domain that we named TPAP. We authenticated the real existence of 106 proteins among the 140 CPs. RNA interference (RNAi) experiments were conducted against 135 CP genes in early- and late-instar nymphs and newly emerged female adults, demonstrating that 32 CPs were essential for BPH normal development or egg production. Combined RNAi experiments suggested redundant and complementary functions of the large number of CPs. Transcriptomic data revealed that the CP genes were expressed in a tissue-specific manner, and there were four clusters of developmental expression patterns. This study gives a comprehensive understanding of the roles of CPs in an insect cuticle.

DDC plays vital roles in the wing spot formation, egg production, and chorion tanning in the brown planthopper.

The gene dopa decarboxylase (Nlddc) of the brown planthopper (BPH, Nilaparvata lugens) was identified in the genome and transcriptome of the insect. The open reading frame of Nlddc is 1,434 bp in length and, it has the potential to encode a protein of 477 amino acid with a conserved pyridoxal-dependent decarboxylase domain and a typical motif, NFNPHKW. Real-time quantification polymerase chain reaction analyses revealed that this gene was highly expressed in the integument and brain, and transcript level peaked in the late stages of egg period and each nymph instar with periodicity. RNA interference results revealed that Nlddc played essential roles in pigment synthesis, formation of wing spot, egg production, and tanning of the chorion. A rapid accumulation of Nlddc transcripts was detected, and it coincided with the injection of the hormone 20-hydroxyecdysone (20E), suggesting that Nlddc transcription was regulated by 20E.

Seminal fluid protein genes of the brown planthopper, Nilaparvata lugens.

BACKGROUND: Seminal fluid proteins (SFPs) are produced mainly in the accessory gland of male insects and transferred to females during mating, in which they induce numerous physiological and post-mating behavioral changes. The brown plant hopper (BPH), Nilaparvata lugens, is an economically important hemipterous pest of rice. The behavior and physiology of the female of this species is significantly altered by mating. SFPs in hemipteran species are still unclear. RESULTS: We applied high-throughput mass spectrometry proteomic analyses to characterize the SFP composition in N. lugens. We identified 94 putative secreted SFPs, and the expression levels of these proteins was determined from the male accessory gland digital gene expression database. The 94 predicted SFPs showed high expression in the male accessory gland. Comparing N. lugens and other insect SFPs, the apparent expansion of N. lugens seminal fluid trypsins and carboxylesterases was observed. The number of N. lugens seminal fluid trypsins (20) was at least twice that in other insects. We detected 6 seminal fluid carboxylesterases in N. lugens seminal fluid, while seminal fluid carboxylesterases were rarely detected in other insects. Otherwise, new insect SFPs, including mesencephalic astrocyte-derived neurotrophic factor, selenoprotein, EGF (epidermal growth factor) domain-containing proteins and a neuropeptide ion transport-like peptide were identified. CONCLUSION: This work represents the first characterization of putative SFPs in a hemipeteran species. Our results provide a foundation for future studies to investigate the functions of SFPs in N. lugens and are an important addition to the available data for comparative studies of SFPs in insects.

A Cripavirus in the brown planthopper, Nilaparvata lugens.

A Cripavirus-like long unique sequence was identified during transcriptome sequencing of the brown planthopper (BPH), Nilaparvata lugens. This unique sequence demonstrated high similarity with the whole-genome sequence of cricket paralysis virus, including 5' and 3' untranslated regions; thus we considered it the whole genome of a new virus. We propose that the virus be named Nilaparvata lugens C virus (NlCV). The plus-strand RNA genome spanned 9144 nt, excluding a 3' poly(A) tail with two large ORFs encoding structural and non-structural proteins, respectively. Detection of NlCV in BPH honeydew raised the hypothesis of horizontal transmission of the virus. Honeydew from viruliferous BPHs was used to feed non-viruliferous insects, the results of which indicated that the BPH could acquire NlCV through feeding and that the virus could multiply in the insect body. A tissue-specific distribution test using real-time quantitative PCR demonstrated that NlCV was mainly present in the reproductive organs, and the virus was detected in eggs laid by viruliferous female insects using nested PCR, indicating the possibility of vertical transmission as well. As no significant symptom was detected in the viruliferous BPH, NlCV is considered a new commensal virus of BPH. Interestingly, this virus was also detected in two other hemipteran insects, the white-backed planthopper and the horned gall aphid, indicating that NlCV might be present in many other hemipteran insects and have a wide host range.

Design and construction of a refrigerator-cooled adiabatic calorimeter for heat capacity measurement in liquid helium temperature region.

Heat capacity is a fundamental thermodynamic property of a substance. Although heat capacity values and related thermodynamic functions are available for many materials, low-temperature heat capacity measurements, especially for novel materials, can still provide valuable insights for research in physics, chemistry, thermodynamics, and other fields. Reliable low-temperature heat capacity data are typically measured using classical adiabatic calorimeters, which use liquid helium as the refrigerant to provide a cryogenic environment for heat capacity measurements. However, liquid helium is not only expensive but also not easy to obtain, which greatly limits the application of adiabatic calorimetry. In this work, an accurate adiabatic calorimeter equipped with a Gifford-MacMahon refrigerator was designed and constructed for measuring the heat capacity of condensed matter in the temperature range from 4 to 100 K. The Gifford-MacMahon refrigerator was utilized to provide a stable liquid helium-free cryogenic environment. A simple mechanical thermal switch assembly was designed to facilitate switching between the refrigeration mode and the adiabatic measurement mode of the calorimeter. Based on the measurement results of standard reference materials, the optimized repeatability and accuracy of heat capacity measurements were determined to be within 0.8% and 1.5%, respectively. The heat capacity of α-Fe2O3 nanoparticles was also investigated with this device. Furthermore, this adiabatic calorimeter only requires electricity to operate in the liquid helium temperature range, which may significantly advance the research on low-temperature heat capacity based on adiabatic calorimetry.

The evolution and functional divergence of 10 Apolipoprotein D-like genes in Nilaparvata lugens.

Apolipoprotein D (ApoD), a member of the lipocalin superfamily of proteins, is involved in lipid transport and stress resistance. Whereas only a single copy of the ApoD gene is found in humans and some other vertebrates, there are typically several ApoD-like genes in insects. To date, there have been relatively few studies that have examined the evolution and functional differentiation of ApoD-like genes in insects, particularly hemi-metabolous insects. In this study, we identified 10 ApoD-like genes (NlApoD1-10) with distinct spatiotemporal expression patterns in Nilaparvata lugens (BPH), which is an important pest of rice. NlApoD1-10 were found to be distributed on 3 chromosomes in a tandem array of NlApoD1/2, NlApoD3-5, and NlApoD7/8, and show sequence and gene structural divergence in the coding regions, indicating that multiple gene duplication events occurred during evolution. Phylogenetic analysis revealed that NlApoD1-10 can be clustered into 5 clades, with NlApoD3-5 and NlApoD7/8 potentially evolving exclusively in the Delphacidae family. Functional screening using an RNA interference approach revealed that only NlApoD2 was essential for BPH development and survival, whereas NlApoD4/5 are highly expressed in testes, and might play roles in reproduction. Moreover, stress response analysis revealed that NlApoD3-5/9, NlApoD3-5, and NlApoD9 were up-regulated after treatment with lipopolysaccharide, H2 O2 , and ultraviolet-C, respectively, indicating their potential roles in stress resistance.

Salivary proteins potentially derived from horizontal gene transfer are critical for salivary sheath formation and other feeding processes.

Herbivorous insects employ an array of salivary proteins to aid feeding. However, the mechanisms behind the recruitment and evolution of these genes to mediate plant-insect interactions remain poorly understood. Here, we report a potential horizontal gene transfer (HGT) event from bacteria to an ancestral bug of Eutrichophora. The acquired genes subsequently underwent duplications and evolved through co-option. We annotated them as horizontal-transferred, Eutrichophora-specific salivary protein (HESPs) according to their origin and function. In Riptortus pedestris (Coreoidea), all nine HESPs are secreted into plants during feeding. The RpHESP4 to RpHESP8 are recently duplicated and found to be indispensable for salivary sheath formation. Silencing of RpHESP4-8 increases the difficulty of R. pedestris in probing the soybean, and the treated insects display a decreased survivability. Although silencing the other RpHESPs does not affect the salivary sheath formation, negative effects are also observed. In Pyrrhocoris apterus (Pyrrhocoroidea), five out of six PaHESPs are secretory salivary proteins, with PaHESP3 being critical for insect survival. The PaHESP5, while important for insects, no longer functions as a salivary protein. Our results provide insight into the potential origin of insect saliva and shed light on the evolution of salivary proteins.

The genomic history and global migration of a windborne pest.

Many insect pests, including the brown planthopper (BPH), undergo windborne migration that is challenging to observe and track. It remains controversial about their migration patterns and largely unknown regarding the underlying genetic basis. By analyzing 360 whole genomes from around the globe, we clarify the genetic sources of worldwide BPHs and illuminate a landscape of BPH migration showing that East Asian populations perform closed-circuit journeys between Indochina and the Far East, while populations of Malay Archipelago and South Asia undergo one-way migration to Indochina. We further find round-trip migration accelerates population differentiation, with highly diverged regions enriching in a gene desert chromosome that is simultaneously the speciation hotspot between BPH and related species. This study not only shows the power of applying genomic approaches to demystify the migration in windborne migrants but also enhances our understanding of how seasonal movements affect speciation and evolution in insects.

Functional analysis of neutral lipases in bug feeding and reproduction.

BACKGROUND: The bean bug, Riptortus pedestris, is known to cause significant economic losses in soybean crops due to its seed-sucking behavior, but the mechanism of its adaptation to lipid-rich seeds remains poorly understood. To exploit potential target genes for controlling this pest, neutral lipases are functionally characterized in this study. RESULTS: In this study, a total of 69 lipases were identified in R. pedestris, including 35 neutral lipases that underwent significant expansion. The phylogeny, expression patterns, and catalytic capacity of neutral lipases were investigated and we selected six salivary gland-specific, eight gut-specific, and three ovary-specific genes for functional analysis. All three ovary-specific neutral lipases (Chr1.3195, Chr1.0994, and Chr5.0087) are critical for insect reproduction, while a few gut-specific neutral lipases (Chr4.0221 and Chr1.3207) influence insect survivorship or weight gain. In contrast, no significant phenotype change is observed when silencing salivary gland-specific neutral lipases. CONCLUSION: The lipases Chr1.3195, Chr1.0994, Chr5.0087, Chr4.0221, and Chr1.3207 are essential for R. pedestris feeding and reproduction, and the insect is highly sensitive to their deficiency, suggesting that neutral lipases are promising candidates for application in RNAi-based control of this destructive pest. © 2023 Society of Chemical Industry.

RNAi-mediated silencing of an egg-specific gene Nllet1 results in hatch failure in the brown planthopper.

BACKGROUND: The brown planthopper (BPH) is one of the most destructive agricultural pests in Asia. RNA interference (RNAi)-mediated pest management has been under development for years, and the selection of appropriate target genes is important for pest-targeted RNAi. C-type lectins (CTLs) are a class of genes that perform a variety of functions, such as the regulation of growth and development. RESULTS: A CTL-S protein named Nllet1, containing a single calcium ion (Ca2+ )-dependent carbohydrate-binding domain (CRD) with a conserved triplet motif QPD was identified and functionally characterized in BPH. Expression profiles at both the transcriptional and translational levels show that Nllet1 accumulates during the serosal cuticle (SC) formation period. Immunofluorescence and immunogold labeling further demonstrated that Nllet1 is located in the serosal endocuticle (en-SC). Maternal RNAi-mediated silencing of Nllet1 disrupted the SC structure, accompanied by a loss of the outward barrier and 100% embryo mortality. Injection of 10 ng dsNllet1 or dsNllet1' per female adult BPH resulted in a total failure of egg hatching. CONCLUSION: Nllet1 is essential for SC formation and embryonic development in BPH, which helps us understand the important roles of CTL-Ss. Additionally, BPH eggs show high sensitivity to the depletion of Nllet1. This study indicates that Nllet1 is a promising candidate gene that can be used to develop RNAi-based control strategies at the BPH egg stage, and it can also be used as a target for developing novel ovicides. © 2022 Society of Chemical Industry.

Planthopper salivary sheath protein LsSP1 contributes to manipulation of rice plant defenses.

Salivary elicitors secreted by herbivorous insects can be perceived by host plants to trigger plant immunity. However, how insects secrete other salivary components to subsequently attenuate the elicitor-induced plant immunity remains poorly understood. Here, we study the small brown planthopper, Laodelphax striatellus salivary sheath protein LsSP1. Using Y2H, BiFC and LUC assays, we show that LsSP1 is secreted into host plants and binds to salivary sheath via mucin-like protein (LsMLP). Rice plants pre-infested with dsLsSP1-treated L. striatellus are less attractive to L. striatellus nymphs than those pre-infected with dsGFP-treated controls. Transgenic rice plants with LsSP1 overexpression rescue the insect feeding defects caused by a deficiency of LsSP1 secretion, consistent with the potential role of LsSP1 in manipulating plant defenses. Our results illustrate the importance of salivary sheath proteins in mediating the interactions between plants and herbivorous insects.

Co-option of a non-retroviral endogenous viral element in planthoppers.

Non-retroviral endogenous viral elements (nrEVEs) are widely dispersed throughout the genomes of eukaryotes. Although nrEVEs are known to be involved in host antiviral immunity, it remains an open question whether they can be domesticated as functional proteins to serve cellular innovations in arthropods. In this study, we found that endogenous toti-like viral elements (ToEVEs) are ubiquitously integrated into the genomes of three planthopper species, with highly variable distributions and polymorphism levels in planthopper populations. Three ToEVEs display exon‒intron structures and active transcription, suggesting that they might have been domesticated by planthoppers. CRISPR/Cas9 experiments revealed that one ToEVE in Nilaparvata lugens, NlToEVE14, has been co-opted by its host and plays essential roles in planthopper development and fecundity. Large-scale analysis of ToEVEs in arthropod genomes indicated that the number of arthropod nrEVEs is currently underestimated and that they may contribute to the functional diversity of arthropod genes.

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

BACKGROUND: 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. RESULTS: 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. CONCLUSION: The results reveal the biological functions of ThrRS in N. lugens in addtion to its 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.

Lateral oviduct-secreted proteins in the brown planthopper.

Oviducts are the "traffic hubs" of the female reproductive system, serving as the crucial conduits for egg transportation. By performing LC-MS/MS proteomic detection together with transcriptomic analysis, 80 lateral oviduct-secreted proteins were identified, and 5 genes (NlOdsp, NlOdsp1, NlOdsp2, NlOdsp3 and NlOdsp4) specifically expressed in the oviducts of the brown planthopper Nilaparvata lugens, the most destructive rice pest, were authenticated. qRT-PCR analysis revealed that these genes and proteins were mainly/specifically expressed in the female reproductive system in adulthood. RNA interference (RNAi) against the 5 NlOdsp genes significantly affected the survival rates (3.4% - 68.7% of the control) and fecundities of female adults (3.9% - 57.6% of the control) at 8 d post injection (p.i.). In addition, the lack of NlOdsp1 caused decreases in the gel-like brown secretions inside the lateral oviducts, while increased secretions were found in the dsNlOdsp2-treated groups. In addition, NlOdsp3 is a pleiotropic gene involved in both oocyte development and egg movement through the lateral oviducts, similar to the role of NlOdsp in egg transportation. The results deepen our understanding of oviduct-secreted proteins in female insects and provide novel target genes for RNAi-based insect pest control. SIGNIFICANCE: Oviduct plays a vital role in animal reproductive processes and it serves as the crucial conduit for egg transportation. Though oviduct secretes have been well documented in high animals, the proteomic information of insect oviduct secretes remains poorly understood. The present study revealed 80 oviduct secreted proteins, including 19 unknown proteins, from the rice planthopper, the most destructive rice pest which lay eggs in plant tissues. Five of the 19 proteins were further functionally characterized. The results not only deepen our understanding of the oviduct secreted proteins in insect reproductive biology, but also provide basis for interaction between insects and host plants, and provide novel target genes for RNAi-based insect pest control.