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.

Endogenous nege-like viral elements in arthropod genomes reveal virus-host coevolution and ancient history of two plant virus families.

Negevirus is a recently proposed taxon of arthropod-infecting virus, which is associated with plant viruses of two families (Virgaviridae and Kitaviridae). Nevertheless, the evolutionary history of negevirus-host and its relationship with plant viruses remain poorly understood. Endogenous nege-like viral elements (ENVEs) are ancient nege-like viral sequences integrated into the arthropod genomes, which can serve as the molecular fossil records of previous viral infection. In this study, 292 ENVEs were identified in 150 published arthropod genomes, revealing the evolutionary history of nege-like viruses and two related plant virus families. We discovered three novel and eight strains of nege-like viruses in 11 aphid species. Further analysis indicated that 10 ENVEs were detected in six aphid genomes, and they were divided into four types (ENVE1-ENVE4). Orthologous integration and phylogenetic analyses revealed that nege-like viruses had a history of infection of over 60 My and coexisted with aphid ancestors throughout the Cenozoic Era. Moreover, two nege-like viral proteins (CP and SP24) were highly homologous to those of plant viruses in the families Virgaviridae and Kitaviridae. CP- and SP24-derived ENVEs were widely integrated into numerous arthropod genomes. These results demonstrate that nege-like viruses have a long-term coexistence with arthropod hosts and plant viruses of the two families, Virgaviridae and Kitaviridae, which may have evolved from the nege-like virus ancestor through horizontal virus transfer events. These findings broaden our perspective on the history of viral infection in arthropods and the origins of plant viruses. IMPORTANCE: Although negevirus is phylogenetically related to plant virus, the evolutionary history of negevirus-host and its relationship with plant virus remain largely unknown. In this study, we used endogenous nege-like viral elements (ENVEs) as the molecular fossil records to investigate the history of nege-like viral infection in arthropod hosts and the evolution of two related plant virus families (Virgaviridae and Kitaviridae). Our results showed the infection of nege-like viruses for over 60 My during the arthropod evolution. ENVEs highly homologous to viral sequences in Virgaviridae and Kitaviridae were present in a wide range of arthropod genomes but were absent in plant genomes, indicating that plant viruses in these two families possibly evolved from the nege-like virus ancestor through cross-species horizontal virus transmission. Our findings provide a new perspective on the virus-host coevolution and the origins of plant viruses.

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.

Intersphincteric Resection Versus Abdominoperineal Resection for Low Rectal Cancer: A Meta-Analysis.

Background. Abdominoperineal resection (APR) has been the standard surgery for ultra-low rectal cancer for a century. In recent years, intersphincteric resection (ISR) has been increasingly used to avoid the permanent colostomy. Up to now, there is no relevant meta-analysis comparing the clinical efficacy of ISR and APR. This meta-analysis aimed to compare the outcomes of these 2 procedures. Methods. A comprehensive search of online databases was performed on PubMed, EMBASE, and the Cochrane Library to obtain comparative studies of ISR and APR. Then the data from studies that met the inclusion criteria were extracted and analyzed. Results. A total of 12 studies covering 2438 patients were included. No significant differences were found between ISR and APR in gender, body mass index, distance from tumor to anal edge, operative time, and blood loss. In addition, hospital stay (weighted mean differences = -2.98 days; 95% confidence interval [CI] = -3.54 to -2.43; P < .00001) and postoperative morbidity (odds ratio [OR] = 0.76; 95% CI = 0.59 to 0.99; P = .04) were significantly lower in ISR group compared with APR group. However, patients who underwent ISR showed lower pathological T-stage (T3T4%, OR = 0.49; 95% CI = 0.28 to 0.86; P = .01) and lymph node metastasis rate (OR = 0.77; 95% CI = 0.59 to 1.01; P = .06) compared with those who underwent APR. Moreover, oncological outcomes were similar between the 2 groups. Conclusion. ISR may provide a safe alternative to APR, with shorter hospital stays, lower postoperative morbidity, and similar oncological outcomes. Well-designed randomized controlled trials are needed to confirm and update the findings of this analysis.

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.

Glove single-port laparoscopy-assisted transanal total mesorectal excision for low rectal cancer: a preliminary report.

PURPOSE: Glove single-port laparoscopy-assisted transanal total mesorectal excision (TaTME) has been successfully carried out in our medical center. The purpose of this study is to evaluate the feasibility of this emerging operation. METHODS: This technique was performed by self-made glove single-port laparoscopic platform to radically resect low rectal cancer. Short-term postoperative results, including complications, length of hospital stay, and follow-up results were collected and analyzed statistically. RESULTS: There are five consecutive patients (three males, two females) who underwent this surgery and included in this study. The mean distance from the tumor to the anal verge was 4.8 cm (range 4.0-6.0). The surgery was completed in all cases, and the rectal tumor was removed successfully without conversion; circumferential margins of all the excised specimens were negative. The mean time of operation was 338.00 min (range 280-400). The average number of lymph node dissection was 12.20. The average postoperative hospital stay was 8.60 days. During the follow-up (14.80 ± 1.92 months), all preventive ileostomies were successfully closed in about 3 months after the surgery, all patients had satisfactory anal function, and no tumor recurrence was found. CONCLUSION: Glove single-port laparoscopy-assisted TaTME has a significant effect in specific patients with low rectal cancer, with rapid recovery and high safety. Prospective randomized studies involving more case counts and long-term follow-up results, especially oncologic outcomes, are needed to validate this technique.

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.

Identification of rapidly induced genes in the response of peanut (Arachis hypogaea) to water deficit and abscisic acid.

BACKGROUND: Peanut (Arachis hypogaea) is an important crop, but droughts often affect peanut production. There is a lack of genomic information available for peanut; therefore, little is known about the molecular basis of its drought stress response. RESULTS: Previously, we found that peanut stomata close rapidly during water deficit and in response to abscisic acid (ABA) treatment, and many genes show changes in their expression levels. To screen for candidate genes involved in the water deficit response, we used the Illumina HiSeq2000/MiSeq sequencing platform to conduct a global transcriptome analysis of peanut seedlings under water deficit with or without an ABA pretreatment. Three peanut tissues (leaves, roots, and stems) collected at each of three developmental stages (four-leaf, flowering, and podding stages) were used to construct sequence libraries. Then, 4.96 × 107 raw sequence reads were generated and the high quality reads were assembled into 47,842 unigenes. We analyzed these sequence libraries to identify differentially expressed genes (DEGs) under water deficit with or without ABA pretreatment. In total, 621 genes were induced rapidly (≥1.5 fold change compared with control) under water deficit, 2,665 genes were induced rapidly under water deficit + ABA pretreatment, and 279 genes overlapped between water deficit and water deficit + ABA pretreatment. Of the 279 overlapping genes, 264 showed the same expression pattern and 15 showed opposite expression patterns. Among the DEGs, 257 were highly induced (>5 fold) by water deficit + ABA pretreatment, while 19 were highly induced (>5 fold) by water deficit alone. The genes induced under water deficit + ABA pretreatment included 100 putative transcription factor (TF) genes, while those induced under water deficit alone included only 22 putative TF genes. To validate the transcriptome results, we conducted quantitative PCR (qPCR) analyses to quantify the transcript levels of nine candidate genes. CONCLUSIONS: The DEGs results show that many genes are rapidly induced in peanut in response to water deficit without or with ABA pretreatment. The results indicate that the main drought response mechanisms in peanut function through an ABA-dependent pathway. Our data provide a comprehensive sequence resource for molecular genetics research on peanut stress responses.

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.

Rapid intracellular acidification is a plant defense response countered by the brown planthopper.

The brown planthopper (BPH) is the most destructive insect pest in rice. Through a stylet, BPH secretes a plethora of salivary proteins into rice phloem cells as a crucial step of infestation. However, how various salivary proteins function in rice cells to promote insect infestation is poorly understood. Among them, one of the salivary proteins is predicted to be a carbonic anhydrase (Nilaparvata lugens carbonic anhydrase [NlCA]). The survival rate of the NlCA-RNA interference (RNAi) BPH insects was extremely low on rice, indicating a vital role of this salivary protein in BPH infestation. We generated NlCA transgenic rice plants and found that NlCA expressed in rice plants could restore the ability of NlCA-RNAi BPH to survive on rice. Next, we produced rice plants expressing the ratiometric pH sensor pHusion and found that NlCA-RNAi BPH induced rapid intracellular acidification of rice cells during feeding. Further analysis revealed that both NlCA-RNAi BPH feeding and artificial lowering of intracellular pH activated plant defense responses and that NlCA-mediated intracellular pH stabilization is linked to diminished defense responses, including reduced callose deposition at the phloem sieve plates and suppressed defense gene expression. Given the importance of pH homeostasis across the kingdoms of life, discovery of NlCA-mediated intracellular pH modulation uncovered a new dimension in the interaction between plants and piercing/sucking insect pests. The crucial role of NlCA for BPH infestation of rice suggests that NlCA is a promising target for chemical or trans-kingdom RNAi-based inactivation for BPH control strategies in plants.

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.