Three RNA helicase DDX genes are essential for the development and oocyte maturation in Laodelphax striatellus.

BACKGROUND: DEAD-box protein (DDX) is a member of the DDX RNA helicase family that exerts multiple functions in RNA metabolism, cell cycle, tumorigenesis, signal pathway, and fertility, particularly in mammals. Nevertheless, the biological functions of DDXs in insects have not been fully resolved and attracted increasing attention these years. Laodelphax striatellus (Hemiptera) is a notorious rice pest through feeding on rice sap and transmitting plant viruses. In this study, we aim to elucidate the functional characterization of DDXs in L. striatellus, and to exploit potential target genes for the development of pest control strategies. RESULTS: In this study, we characterized the expression patterns of LsDDX6, LsDDX47, and LsDDX51 in planthoppers and analyzed their conserved motifs. These genes were found to be expressed in all tissues and developmental stages examined, with significantly higher transcript levels observed in the ovary. Knockdown of LsDDX6, LsDDX47, and LsDDX51 resulted in an obvious lethal phenotype in nymphs and abnormal ovarian development in adults. Furthermore, a total of 27 DDXs were identified in L. striatellus, and most DDXs were highly expressed in ovary and structure analysis result revealed that all of the DDXs possessed nine motifs that were unique to the DDX family. CONCLUSION: The three DDX RNA helicases (LsDDX6, LsDDX47, and LsDDX51) are essential for both survivorship and reproduction in L. striatellus. Considering a total number of 27 DDXs identified in L. striatellus, they might serve as promising candidates for application in RNAi-based control of this destructive pest. © 2024 Society of Chemical Industry.

Three-dimensional reconstruction of insect chemosensory sensillum.

The olfactory system is involved in food and mate recognition in insects. However, 3D structures of chemosensory sensilla in insects are unexplored yet. Here, the internal structures of an olfactory sensillum on the antenna of the brown planthopper, Nilaparvata lugens (Hemiptera: Delphacidae), one of the most important rice pests, are examined and imaged using focused ion beam scanning electron microscopy. Based on these images, a 3D structure is reconstructed in this study. We find that the trichoid olfactory sensillum possesses a multiporous wall encircling a lumen with one sensory cell. Besides, there are three accessory cells (ACs) and a glia cell with different cell contents surrounding the sensory cell. The abundant tubular membrane structures in the tormogen cell suggest its role in secreting proteins like odorant binding proteins into the receptor lymph, while three auxiliary cells with simpler cellular content closely enfold the sensory cell, probably to prevent leaking of the receptor lymph into the surrounding epidermis. In the sensory cell, the microtubules and two tandem basal bodies at the base of the microtubules are also reconstructed. They are considered as a propulsive engine to ensure dendrite vibration or spinning in the receptor lymph, so that the proteins and odorant molecules move faster in the receptor lymph, which improves recognition of environmental odors and enables the insect to immediately respond to this information.

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.

Genetic Characterization of Two Novel Insect-Infecting Negative-Sense RNA Viruses Identified in a Leaf Beetle, Aulacophora indica.

Herbivorous insects harbor a variety of insect-specific viruses (ISVs) some of which are considered to be valuable biological agents for potential applications in biological defense and control strategies. Leaf beetles with chewing mouthparts are particularly known for their capacity to disrupt plant tissue while feeding, often creating openings that can act as entry points for plant pathogens. In this study, we have identified two new negative-sense RNA viruses infecting the leaf beetle Aulacophora indica, an important member of the Chrysomelidae family. These recently discovered viruses belong to the viral families Nyamiviridae and Chuviridae and have been preliminarily named Aulacophora indica nyami-like virus 1 (AINlV1) and Aulacophora indica chu-like virus 1 (AIClV1), respectively. The complete genomic sequences of these viruses were obtained using rapid amplification of cDNA ends (RACE) techniques. Detailed analysis of their genomic structures has confirmed their similarity to other members within their respective families. Furthermore, analysis of virus-derived small interfering RNA (vsiRNA) demonstrated a high abundance and typical vsiRNA pattern of AINlV1 and AIClV1, offering substantial evidence to support their classification as ISVs. This research enhances our understanding of viral diversity within insects.

Complete genome sequence of a novel amalgavirus in sponge gourd, Luffa cylindrica.

A novel monopartite dsRNA virus, tentatively named "sponge gourd amalgavirus 1" (SGAV1), was discovered by high-throughput sequencing in sponge gourd (Luffa cylindrica) displaying mosaic symptoms in Jiashan County, Zhejiang Province, China. The genome of SGAV1 is 3,447 nucleotides in length and contains partially overlapping open reading frames (ORFs) encoding a putative replication factory matrix-like protein and a fusion protein, respectively. The fusion protein of SGAV1 shares 57.07% identity with the homologous protein of salvia miltiorrhiza amalgavirus 1 (accession no. DAZ91057.1). Phylogenetic analysis based on the RNA-dependent RNA polymerase (RdRp) protein suggests that SGAV1 belongs to the genus Amalgavirus of the family Amalgaviridae. Moreover, analysis of SGAV1-derived small interfering RNAs indicated that SGAV1 was actively replicating in the host plant. Semi-quantitative RT-PCR showed higher levels of SGAV1 expression in leaves than in flowers and fruits. This is the first report of a novel amalgavirus found in sponge gourd in China.

Identification and Characterization of Three Novel Solemo-like Viruses in the White-Backed Planthopper, Sogatella furcifera.

Agricultural insects play a crucial role in transmitting plant viruses and host a considerable number of insect-specific viruses (ISVs). Among these insects, the white-backed planthoppers (WBPH; Sogatella furcifera, Hemiptera: Delphacidae) are noteworthy rice pests and are responsible for disseminating the southern rice black-streaked dwarf virus (SRBSDV), a significant rice virus. In this study, we analyzed WBPH transcriptome data from public sources and identified three novel viruses. These newly discovered viruses belong to the plant-associated viral family Solemoviridae and were tentatively named Sogatella furcifera solemo-like virus 1-3 (SFSolV1-3). Among them, SFSolV1 exhibited a prevalent existence in different laboratory populations, and its complete genome sequence was obtained using rapid amplification of cDNA ends (RACE) approaches. To investigate the antiviral RNA interference (RNAi) response in WBPH, we conducted an analysis of virus-derived small interfering RNAs (vsiRNAs). The vsiRNAs of SFSolV1 and -2 exhibited typical patterns associated with the host's siRNA-mediated antiviral immunity, with a preference for 21- and 22-nt vsiRNAs derived equally from both the sense and antisense genomic strands. Furthermore, we examined SFSolV1 infection and distribution in WBPH, revealing a significantly higher viral load of SFSolV1 in nymphs' hemolymph compared to other tissues. Additionally, in adult insects, SFSolV1 exhibited higher abundance in male adults than in female adults.

Complete genome sequence and genetic characterization of a novel segmented RNA virus infecting Nilaparvata lugens.

The brown planthopper (BPH), Nilaparvata lugens, is a significant agricultural pest capable of long-distance migration and transmission of viruses that cause severe disease in rice. In this study, we identified a novel segmented RNA virus in a BPH, and this virus exhibited a close relationship to members of a recently discovered virus lineage known as "quenyaviruses" within the viral kingdom Orthornavirae. This newly identified virus was named "Nilaparvata lugens quenyavirus 1" (NLQV1). NLQV1 consists of five positive-sense, single-stranded RNAs, with each segment containing a single open reading frame (ORF). The genomic characteristics and phylogenetic analysis support the classification of NLQV1 as a novel quenyavirus. Notably, all of the genome segments of NLRV contained the 5'-terminal sequence AUCUG. The characteristic virus-derived small interfering RNA (vsiRNA) profile of NLQV1 suggests that the antiviral RNAi pathway of the host BPH was activated in response to virus infection. These findings represent the first documented report of quenyaviruses in planthoppers, contributing to our understanding of quenyaviruses and expanding our knowledge of insect-specific viruses in planthoppers.

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.

Complete genome analysis of a novel narnavirus in sweet viburnum (Viburnum odoratissimum).

Trees and shrubs provide important ecological services. However, few studies have surveyed the virome in trees and shrubs. In this study, we discovered a new positive-sense RNA virus originating from Viburnum odoratissimum, which we named "Vo narna-like virus". The complete genome of Vo narna-like virus is 3,451 nt in length with an open reading frame (ORF) encoding the RNA-dependent RNA polymerase (RdRP) protein. Phylogenetic analysis placed this virus within the betanarnavirus clade, sharing 53.63% amino acid sequence identity with its closest relative, Qingdao RNA virus 2. The complete sequence of the virus was confirmed by rapid amplification of cDNA ends (RACE) and Sanger sequencing. Small interfering RNA (siRNA) analysis indicated that this virus interacts with the RNA interference (RNAi) pathway of V. odoratissimum. This is the first report of a narnavirus in V. odoratissimum.

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.

Molecular and biological characterization of a bunyavirus infecting the brown planthopper (Nilaparvata lugens).

A negative-strand symbiotic RNA virus, tentatively named Nilaparvata lugens Bunyavirus (NLBV), was identified in the brown planthopper (BPH, Nilaparvata lugens). Phylogenetic analysis indicated that NLBV is a member of the genus Mobuvirus (family Phenuiviridae, order Bunyavirales). Analysis of virus-derived small interfering RNA suggested that antiviral immunity of BPH was successfully activated by NLBV infection. Tissue-specific investigation showed that NLBV was mainly accumulated in the fat-body of BPH adults. Moreover, NLBV was detected in eggs of viruliferous female BPHs, suggesting the possibility of vertical transmission of NLBV in BPH. Additionally, no significant differences were observed for the biological properties between NLBV-infected and NLBV-free BPHs. Finally, analysis of geographic distribution indicated that NLBV may be prevalent in Southeast Asia. This study provided a comprehensive characterization on the molecular and biological properties of a symbiotic virus in BPH, which will contribute to our understanding of the increasingly discovered RNA viruses in insects.

Inhibition of Rice Stripe Virus Accumulation by Polyubiquitin-C in Laodelphax striatellus.

Many hosts utilize the ubiquitin system to defend against viral infection. As a key subunit of the ubiquitin system, the role of polyubiquitin in the viral infection of insects is unclear. Here, we identified the full-length cDNA of the polyubiquitin-C (UBC) gene in Laodelphax striatellus, the small brown planthopper (SBPH). LsUBC was expressed in various tissues and was highly expressed in salivary glands, midgut, and reproductive systems. Furthermore, the LsUBC expression profiles in the developmental stages showed that LsUBC was ubiquitously expressed in seven developmental stages and was highest expressed in female adults with SBPH. qRT-PCR analyses indicated that rice stripe virus (RSV) infection promoted the LsUBC expression. Knockdown of LsUBC mRNA via RNA interference increased RSV accumulation. These findings suggest that LsUBC inhibits RSV accumulation in L. striatellus.

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.

Maintenance of persistent transmission of a plant arbovirus in its insect vector mediated by the Toll-Dorsal immune pathway.

Throughout evolution, arboviruses have developed various strategies to counteract the host's innate immune defenses to maintain persistent transmission. Recent studies have shown that, in addition to bacteria and fungi, the innate Toll-Dorsal immune system also plays an essential role in preventing viral infections in invertebrates. However, whether the classical Toll immune pathway is involved in maintaining the homeostatic process to ensure the persistent and propagative transmission of arboviruses in insect vectors remain unclear. In this study, we revealed that the transcription factor Dorsal is actively involved in the antiviral defense of an insect vector (Laodelphax striatellus) by regulating the target gene, zinc finger protein 708 (LsZN708), which mediates downstream immune-related effectors against infection with the plant virus (Rice stripe virus, RSV). In contrast, an antidefense strategy involving the use of the nonstructural-protein (NS4) to antagonize host antiviral defense through competitive binding to Dorsal from the MSK2 kinase was employed by RSV; this competitive binding inhibited Dorsal phosphorylation and reduced the antiviral response of the host insect. Our study revealed the molecular mechanism through which Toll-Dorsal-ZN708 mediates the maintenance of an arbovirus homeostasis in insect vectors. Specifically, ZN708 is a newly documented zinc finger protein targeted by Dorsal that mediates the downstream antiviral response. This study will contribute to our understanding of the successful transmission and spread of arboviruses in plant or invertebrate hosts.

Silencing NlFAR7 destroyed the pore canals and related structures of the brown planthopper.

Fatty acyl-CoA reductase (FAR) is one of the key enzymes, which catalyses the conversion of fatty acyl-CoA to the corresponding alcohols. Among the FAR family members in the brown planthopper (Nilaparvata lugens), NlFAR7 plays a pivotal role in both the synthesis of cuticular hydrocarbons and the waterproofing of the cuticle. However, the precise mechanism by which NlFAR7 influences the formation of the cuticle structure in N. lugens remains unclear. Therefore, this paper aims to investigate the impact of NlFAR7 through RNA interference, transmission electron microscope, focused ion beam scanning electron microscopy (FIB-SEM) and lipidomics analysis. FIB-SEM is employed to reconstruct the three-dimensional (3D) architecture of the pore canals and related cuticle structures in N. lugens subjected to dsNlFAR7 and dsGFP treatments, enabling a comprehensive assessment of changes in the cuticle structures. The results reveal a reduction in the thickness of the cuticle and disruptions in the spiral structure of pore canals, accompanied by widened base and middle diameters. Furthermore, the lipidomics comparison analysis between dsNlFAR7- and dsGFP-treated N. lugens demonstrated that there were 25 metabolites involved in cuticular lipid layer synthesis, including 7 triacylglycerols (TGs), 5 phosphatidylcholines (PCs), 3 phosphatidylethanolamines (PEs) and 2 diacylglycerols (DGs) decreased, and 4 triacylglycerols (TGs) and 4 PEs increased. In conclusion, silencing NlFAR7 disrupts the synthesis of overall lipids and destroys the cuticular pore canals and related structures, thereby disrupting the secretion of cuticular lipids, thus affecting the cuticular waterproofing of N. lugens. These findings give significant attention with reference to further biochemical researches on the substrate specificity of FAR protein, and the molecular regulation mechanisms during N. lugens life cycle.

Molecular Characterization of an Isolate of Bean Common Mosaic Virus First Identified in Gardenia Using Metatranscriptome and Small RNA Sequencing.

Gardenia (Gardenia jasminoides) is a popular and economically vital plant known for its ornamental and medicinal properties. Despite its widespread cultivation, there has been no documentation of plant viruses on gardenia yet. In the present study, gardenia leaves exhibiting symptoms of plant viral diseases were sampled and sequenced by both metatranscriptome and small RNA sequencing. As a consequence, bean common mosaic virus (BCMV) was identified in gardenia for the first time and named BCMV-gardenia. The full genome sequence of BCMV-gardenia is 10,054 nucleotides (nt) in length (excluding the poly (A) at the 3' termini), encoding a large polyprotein of 3,222 amino acids. Sequence analysis showed that the N-termini of the polyprotein encoded by BCMV-gardenia is less conserved when compared to other BCMV isolates, whereas the C-termini is the most conserved. Maximum likelihood phylogenetic analysis showed that BCMV-gardenia was clustered closely with other BCMV isolates identified outside the leguminous plants. Our results indicated that the majority of BCMV-gardenia virus-derived small interfering RNAs (vsiRNAs) were 21 nt and 22 nt, with 21 nt being more abundant. The first nucleotide at the 5' termini of vsiRNAs derived from BCMV-gardenia preferred U and A. The ratio of vsiRNAs derived from sense (51.1%) and antisense (48.9%) strands is approaching, and the distribution of vsiRNAs along the viral genome is generally even, with some hot spots forming in local regions. Our findings could provide new insights into the diversity, evolution, and host expansion of BCMV and contribute to the prevention and treatment of this virus.

Complete genome sequence of a novel robigovirus infecting Mentha arvensis.

The complete genomic sequence of a novel robigovirus, provisionally named "Mentha arvensis robigovirus 1" (MARV1), was determined by combining next-generation sequencing (NGS), reverse transcription polymerase chain reaction (RT-PCR), and rapid amplification of cDNA ends (RACE) PCR. The complete genomic sequence of this new virus is 7617 nucleotides in length, excluding the 3' poly(A) tail. The MARV1 genome encodes a putative replicase, "triple gene block" proteins, and a coat protein. Phylogenetic analysis demonstrated that MARV1 is a member of the genus Robigovirus, with closest relationships to African oil palm ringspot virus (AOPRV). Furthermore, MARV1-derived small interfering RNAs (siRNAs) showed typical patterns of plant-virus-derived siRNAs produced by the host antiviral RNA interference pathway. This is the first report of a plant virus of the genus Robigovirus in M. arvensis.

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.

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.

Chromosome-level Genome Assembly and Sex-specific Differential Transcriptome of the White-backed Planthopper, Sogatella furcifera.

Background: The white-backed planthopper (WBPH), Sogatella furcifera, causes great damage to many crops (mainly rice) by direct feeding or transmitting plant viruses. The previous genome assembly was generated by second-generation sequencing technologies, with a contig N50 of only 51.5 kb, and contained a lot of heterozygous sequences. Methods: We utilized third-generation sequencing technologies and Hi-C data to generate a high-quality chromosome-level assembly. We also provide a large amount of transcriptome data for full-length transcriptome analysis and gender differential expression analysis. Results: The final assembly comprised 56.38 Mb, with a contig N50 of 2.20 Mb and a scaffold N50 of 45.25 Mb. Fourteen autosomes and one X chromosome were identified. More than 99.5% of the assembled bases located on the 15 chromosomes. 95.9% of the complete BUSCO Hemiptera genes were detected in the final assembly and 16,880 genes were annotated. 722 genes were relatively highly expressed in males, while 60 in the females. Conclusion: The integrated genome, definite sex chromosomes, comprehensive transcriptome profiles, high efficiency of RNA interference and short life cycle substantially made WBPH an efficient research object for functional genomics.