Parasitoid Serpins Evolve Novel Functions to Manipulate Host Homeostasis.

Parasitoids introduce various virulence factors when parasitism occurs, and some taxa generate teratocytes to manipulate the host immune system and metabolic homeostasis for the survival and development of their progeny. Host-parasitoid interactions are extremely diverse and complex, yet the evolutionary dynamics are still poorly understood. A category of serpin genes, named CvT-serpins, was discovered to be specifically expressed and secreted by the teratocytes of Cotesia vestalis, an endoparasitoid of the diamondback moth Plutella xylostella. Genomic and phylogenetic analysis indicated that the C. vestalis serpin genes are duplicated and most of them are clustered into 1 monophyletic clade. Intense positive selection was detected at the residues around the P1-P1' cleavage sites of the Cv-serpin reactive center loop domain. Functional analyses revealed that, in addition to the conserved function of melanization inhibition (CvT-serpins 1, 16, 18, and 21), CvT-serpins exhibited novel functions, i.e. bacteriostasis (CvT-serpins 3 and 5) and nutrient metabolism regulation (CvT-serpins 8 and 10). When the host-parasitoid system is challenged with foreign bacteria, CvT-serpins act as an immune regulator to reprogram the host immune system through sustained inhibition of host melanization while simultaneously functioning as immune effectors to compensate for this suppression. In addition, we provided evidence that CvT-serpin8 and 10 participate in the regulation of host trehalose and lipid levels by affecting genes involved in these metabolic pathways. These findings illustrate an exquisite tactic by which parasitoids win out in the parasite-host evolutionary arms race by manipulating host immune and nutrition homeostasis via adaptive gene evolution and neofunctionalization.

Bracoviruses recruit host integrases for their integration into caterpillar's genome.

Some DNA viruses infect host animals usually by integrating their DNAs into the host genome. However, the mechanisms for integration remain largely unknown. Here, we find that Cotesia vestalis bracovirus (CvBV), a polydnavirus of the parasitic wasp C. vestalis (Haliday), integrates its DNA circles into host Plutella xylostella (L.) genome by two distinct strategies, conservatively and randomly, through high-throughput sequencing analysis. We confirmed that the conservatively integrating circles contain an essential "8+5" nucleotides motif which is required for integration. Then we find CvBV circles are integrated into the caterpillar's genome in three temporal patterns, the early, mid and late stage-integration. We further identify that three CvBV-encoded integrases are responsible for some, but not all of the virus circle integrations, indeed they mainly participate in the processes of early stage-integration. Strikingly, we find two P. xylostella retroviral integrases (PxIN1 and PxIN2) are highly induced upon wasp parasitism, and PxIN1 is crucial for integration of some other early-integrated CvBV circles, such as CvBV_04, CvBV_12 and CvBV_24, while PxIN2 is important for integration of a late-integrated CvBV circle, CvBV_21. Our data uncover a novel mechanism in which CvBV integrates into the infected host genome, not only by utilizing its own integrases, but also by recruiting host enzymes. These findings will strongly deepen our understanding of how bracoviruses regulate and integrate into their hosts.

Symbiotic bracovirus of a parasite manipulates host lipid metabolism via tachykinin signaling.

Parasites alter host energy homeostasis for their own development, but the mechanisms underlying this phenomenon remain largely unknown. Here, we show that Cotesia vestalis, an endoparasitic wasp of Plutella xylostella larvae, stimulates a reduction of host lipid levels. This process requires excess secretion of P. xylostella tachykinin (PxTK) peptides from enteroendocrine cells (EEs) in the midgut of the parasitized host larvae. We found that parasitization upregulates PxTK signaling to suppress lipogenesis in midgut enterocytes (ECs) in a non-cell-autonomous manner, and the reduced host lipid level benefits the development of wasp offspring and their subsequent parasitic ability. We further found that a C. vestalis bracovirus (CvBV) gene, CvBV 9-2, is responsible for PxTK induction, which in turn reduces the systemic lipid level of the host. Taken together, these findings illustrate a novel mechanism for parasite manipulation of host energy homeostasis by a symbiotic bracovirus gene to promote the development and increase the parasitic efficiency of an agriculturally important wasp species.

A high-quality genome of the dobsonfly Neoneuromus ignobilis reveals molecular convergences in aquatic insects.

Neoneuromus ignobilis is an archaic holometabolous aquatic predatory insect. However, a lack of genomic resources hinders the use of whole genome sequencing to explore their genetic basis and molecular mechanisms for adaptive evolution. Here, we provided a high-contiguity, chromosome-level genome assembly of N. ignobilis using high coverage Nanopore and PacBio reads with the Hi-C technique. The final assembly is 480.67 MB in size, containing 12 telomere-ended pseudochromosomes with only 17 gaps. We compared 42 hexapod species genomes including six independent lineages comprising 11 aquatic insects, and found convergent expansions of long wavelength-sensitive and blue-sensitive opsins, thermal stress response TRP channels, and sulfotransferases in aquatic insects, which may be related to their aquatic adaptation. We also detected strong nonrandom signals of convergent amino acid substitutions in aquatic insects. Collectively, our comparative genomic analysis revealed the evidence of molecular convergences in aquatic insects during both gene family evolution and convergent amino acid substitutions.

The mitochondrial genome of Chelonus formosanus (Hymenoptera: Braconidae) with novel gene orders and phylogenetic implications.

Chelonus formosanus Sonan is an important egg-larval parasitoid of noctuid moths and a potential candidate for understanding interactions between host and parasitoid mediated by polydnavirues (PDVs). We sequenced and annotated the mitochondrial genome of C. formosanus, which is 15,466 bp in length and possesses 38 mitochondrial genes. However, unlike most animal mitochondrial genomes, it contains one extra trnF gene. There are five transfer RNA (tRNA) rearrangement events compared with the ancestral gene order, which is a novel rearrangement type in Hymenoptera for all published mitogenomes so far. Phylogenetic trees supported C. formosanus from the subfamily Cheloninae was closely related to the subfamily Cardiochilinae and Microgastrinae.

The genomes of two parasitic wasps that parasitize the diamondback moth.

BACKGROUND: Parasitic insects are well-known biological control agents for arthropod pests worldwide. They are capable of regulating their host's physiology, development and behaviour. However, many of the molecular mechanisms involved in host-parasitoid interaction remain unknown. RESULTS: We sequenced the genomes of two parasitic wasps (Cotesia vestalis, and Diadromus collaris) that parasitize the diamondback moth Plutella xylostella using Illumina and Pacbio sequencing platforms. Genome assembly using SOAPdenovo produced a 178 Mb draft genome for C. vestalis and a 399 Mb draft genome for D. collaris. A total set that contained 11,278 and 15,328 protein-coding genes for C. vestalis and D. collaris, respectively, were predicted using evidence (homology-based and transcriptome-based) and de novo prediction methodology. Phylogenetic analysis showed that the braconid C. vestalis and the ichneumonid D. collaris diverged approximately 124 million years ago. These two wasps exhibit gene gains and losses that in some cases reflect their shared life history as parasitic wasps and in other cases are unique to particular species. Gene families with functions in development, nutrient acquisition from hosts, and metabolism have expanded in each wasp species, while genes required for biosynthesis of some amino acids and steroids have been lost, since these nutrients can be directly obtained from the host. Both wasp species encode a relative higher number of neprilysins (NEPs) thus far reported in arthropod genomes while several genes encoding immune-related proteins and detoxification enzymes were lost in both wasp genomes. CONCLUSIONS: We present the annotated genome sequence of two parasitic wasps C. vestalis and D. collaris, which parasitize a common host, the diamondback moth, P. xylostella. These data will provide a fundamental source for studying the mechanism of host control and will be used in parasitoid comparative genomics to study the origin and diversification of the parasitic lifestyle.

Safety, efficacy, and pharmacokinetics of nirmatrelvir and ritonavir in patients with severe COVID-19 and renal impairment: A case report.

Nirmatrelvir/ritonavir (N/r) has received emergency use authorization for mild-to-moderate COVID-19 treatment in adult and pediatric patients (aged and weighing at least 12 years and 40 kg, respectively) presenting positive direct SARS-CoV-2 viral testing results and a high risk of disease progression to severe COVID-19. However, information remains limited concerning the corresponding drug safety, efficacy, and pharmacokinetics in patients with severe renal impairment. In this study, we present the case of a 91-year-old Chinese man who, despite exhibiting recurrent positive SARS-CoV-2 results and progression to severe COVID-19, was treated with N/r. Due to severe renal impairment and concurrent administration of continuous renal replacement therapy (continuous venovenous hemofiltration) during medication, we aimed to determine the serum N/r drug concentration in the patient. Our analysis revealed Cmax values of 12.42 and 2.001 µg/mL for nirmatrelvir and ritonavir, respectively. Despite the particularly high serum N/r concentration in this patient, the clinical and laboratory test analyses confirmed that the treatment was safe and effective. Nevertheless, N/r should be used with caution and at lower doses in patients with severe renal impairment to avoid potential high N/r concentration-related adverse reactions and events.

A chromosome-level genome assembly of the gall maker pest inquiline, Diomorus aiolomorphi Kamijo (Hymenoptera: Torymidae).

Diomorus aiolomorphi Kamijo (Hymenoptera: Torymidae) is an inquiline of gall maker Aiolomorphus rhopaloides Walker (Hymenoptera: Eurytomidae). They are of significant economic significance and predominantly inhabit bamboo forest. So far, only four scaffold-level genomes have been published for the family Torymidae. In this study, we present a high-quality genome assembly of D. aiolomorphi at the chromosome level, achieved through the integration of Nanopore (ONT) long-read, Illumina pair-end DNA short-read, and High-through Chromosome Conformation Capture (Hi-C) sequencing methods. The final assembly was 1,084.56 Mb in genome size, with 1,083.41 Mb (99.89%) assigned to five pseudochromosomes. The scaffold N50 length reached 224.87 Mb, and the complete Benchmarking Universal Single-Copy Orthologs (BUSCO) score was 97.3%. The genome contained 762.12 Mb of repetitive elements, accounting for 70.27% of the total genome size. A total of 18,011 protein-coding genes were predicted, with 17,829 genes being functionally annotated. The high-quality genome assembly of D. aiolomorphi presented in this study will serve as a valuable genomic resource for future research on parasitoid wasps. The results of this study may also contribute to the development of biological control strategies for pest management in bamboo forests, enhancing ecological balance and economic sustainability.

Chromosome-level genome assembly of Microplitis manilae Ashmead, 1904 (Hymenoptera: Braconidae).

Microplitis manilae Ashmead (Hymenoptera: Braconidae) is an important parasitoid of agricultural pests in lepidopteran species. So far, two extant genome assembles from the genus Microplitis are fragmented. Here, we offered a high-quality genome assembly of M. manilae at the chromosome level with high accuracy and contiguity, assembled by ONT long-read, MGI-SEQ short-read, and Hi-C sequencing methods. The final assembled genome size was 282.85 Mb, with 268.17 Mb assigned to 11 pseudochromosomes. The scaffold N50 length was 25.23 Mb, and the complete BUSCO score was 98.61%. The genome contained 152.37 Mb of repetitive elements, representing 53.87% of the total genome size. We predicted 15,689 protein-coding genes, of which 13,580 genes were annotated functionally. Gene family evolution investigations of M. manilae revealed 615 expanded and 635 contracted gene families. The high-quality genome of M. manilae reported in this paper will be a useful genomic resource for research on parasitoid wasps in the future.

A new gene family (BAPs) of Cotesia bracovirus induces apoptosis of host hemocytes.

Polydnaviruses (PDVs), obligatory symbionts with parasitoid wasps, function as host immune suppressors and growth and development regulator. PDVs can induce host haemocyte apoptosis, but the underlying mechanism remains largely unknown. Here, we provided evidence that, during the early stages of parasitism, the activated Cotesia vestalis bracovirus (CvBV) reduced the overall number of host haemocytes by inducing apoptosis. We found that one haemocyte-highly expressed CvBV gene, CvBV-26-4, could induce haemocyte apoptosis. Further analyses showed that CvBV-26-4 has four homologs from other Cotesia bracoviruses and BV from wasps in the genus Glyptapanteles, and all four of them possessed a similar structure containing 3 copies of a well-conserved motif (Gly-Tyr-Pro-Tyr, GYPY). Mass spectrometry analysis revealed that CvBV-26-4 was secreted into plasma by haemocytes and then degraded into peptides that induced the apoptosis of haemocytes. Moreover, ectopic expression of CvBV-26-4 caused fly haemocyte apoptosis and increased the susceptibility of flies to bacteria. Based on this research, a new family of bracovirus genes, Bracovirus apoptosis-inducing proteins (BAPs), was proposed. Furthermore, it was discovered that the development of wasp larvae was affected when the function of CvBV BAP was obstructed in the parasitized hosts. The results of our study indicate that the BAP gene family from the bracoviruses group is crucial for immunosuppression during the early stages of parasitism.

Chromosome-level genome assembly of Chouioia cunea Yang, the parasitic wasp of the fall webworm.

Chouioia cunea Yang 1989 is a parasitic wasp of many lepidopteran insects during their pupal stage, and has been successfully used to control pests such as the fall webworm Hyphantria cunea. Here we reported the chromosome-level genome of C. cunea by using short (MGI-SEQ), long (Oxford Nanopore), chromatin-linked (Hi-C) sequencing reads and transcriptomic data, representing the first chromosome-level genome of parasitic wasps of the family Eulophidae. The total assembly length is 171.99 Mb, containing 6 pesudo-chromosomes with a GC content of 36.89% and the scaffold/contig N50 length of 31.70/26.52 Mb. The BUSCO completeness of the assembly was estimated to be 98.7%. A total of 12,258 protein-coding genes (PCGs), 10,547 3'-UTRs, and 10,671 5'-UTRs were annotated. This high-quality genome is an important step toward a better understanding of the genomes of the Eulophidae (Chalcidoidea), and will serve as a valuable resource for analyses of phylogenetic relationships and the evolution of Hymenoptera.

Virus and endogenous viral element-derived small non-coding RNAs and their roles in insect-virus interaction.

RNA interference pathways mediated by different types of small non-coding RNAs (siRNAs, miRNAs and piRNAs) are conserved biological responses to exotic stresses, including viral infection. Aside from the well-established siRNA pathway, the miRNA pathway and the piRNA pathway process viral sequences, exogenously or endogenously, into miRNAs and piRNAs, respectively. During the host-virus interaction, viral sequences, including both coding and non-coding sequences, can be integrated as endogenous viral elements (EVEs) and thereby become present within the germline of a non-viral organism. In recent years, significant progress has been made in characterizing the biogenesis and function of viruses and EVEs associated with snRNAs. Overall, the siRNA pathway acts as the primarily antiviral defense against a wide range of exogenous viruses; the miRNA pathways associated with viruses or EVEs function in antiviral response and host gene regulation; EVE derived piRNAs with a ping-pong signature have the potential to limit cognate viral infection.

The chromosome-level genome of Chinese praying mantis Tenodera sinensis (Mantodea: Mantidae) reveals its biology as a predator.

BACKGROUND: The Chinese praying mantis, Tenodera sinensis (Saussure), is a carnivorous insect that preys on a variety of arthropods and small vertebrates, including pest species. Several studies have been conducted to understand its behavior and physiology. However, there is limited knowledge about the genetic information underlying its genome evolution, digestive demands, and predatory behaviors. FINDINGS: Here we have assembled the chromosome-level genome of T. sinensis, representing the first sequenced genome of the family Mantidae, with a genome size of 2.54 Gb and scaffold N50 of 174.78 Mb. Our analyses revealed that 98.6% of BUSCO genes are present, resulting in a well-annotated assembly compared to other insect genomes, containing 25,022 genes. The reconstructed phylogenetic analysis showed the expected topology placing the praying mantis in an appropriate position. Analysis of transposon elements suggested the Gypsy/Dirs family, which belongs to long terminal repeat (LTR) transposons, may be a key factor resulting in the larger genome size. The genome shows expansions in several digestion and detoxification associated gene families, including trypsin and glycosyl hydrolase (GH) genes, ATP-binding cassette (ABC) transporter, and carboxylesterase (CarE), reflecting the possible genomic basis of digestive demands. Furthermore, we have found 1 ultraviolet-sensitive opsin and 2 long-wavelength-sensitive (LWS) opsins, emphasizing the core role of LWS opsins in regulating predatory behaviors. CONCLUSIONS: The high-quality genome assembly of the praying mantis provides a valuable repository for studying the evolutionary patterns of the mantis genomes and the gene expression profiles of insect predators.

Characterization of Molting Process during the Different Developmental Stages of the Diamondback Moth Plutella xylostella.

The molting process of the lepidopteran insects is observed for many species. However, the detailed description of the morphological transformation and behavioral sequence during molting are rarely provided and visualized. Here, we described the molting process of the diamondback moth Plutella xylostella by providing the duration and photographic details of staging criteria of each stage using stereo microscopy and a digital video camera. We divided the morphological transformation of egg development and hatching into five stages, the larval-larval ecdysis and the larval-pupal metamorphosis into five stages, the pupal development and eclosion into three stages, and the post-eclosion behavior into four stages. Several new characters in the molting process that were not previously described in other lepidopteran insects were found, i.e., the larvae contracted anterior-posteriorly then dorsal-ventrally during pre-ecdysis, and the antennae waved backward then forward in the post-eclosion behavior. Our findings will deepen the knowledge of the molting biology of lepidopteran insects and facilitate the study of the underlying mechanisms.

The Dual Functions of a Bracovirus C-Type Lectin in Caterpillar Immune Response Manipulation.

Parasitoids are widespread in natural ecosystems and normally equipped with diverse viral factors to defeat host immune responses. On the other hand, parasitoids can enhance the antibacterial abilities and improve the hypoimmunity traits of parasitized hosts that may encounter pathogenic infections. These adaptive strategies guarantee the survival of parasitoid offspring, yet their underlying mechanisms are poorly understood. Here, we focused on Cotesia vestalis, an endoparasitoid of the diamondback moth Plutella xylostella, and found that C. vestalis parasitization decreases the number of host hemocytes, leading to disruption of the encapsulation reaction. We further found that one bracovirus C-type lectin gene, CvBV_28-1, is highly expressed in the hemocytes of parasitized hosts and participates in suppressing the proliferation rate of host hemocytes, which in turn reduces their population and represses the process of encapsulation. Moreover, CvBV_28-1 presents a classical bacterial clearance ability via the agglutination response in a Ca2+-dependent manner in response to gram-positive bacteria. Our study provides insights into the innovative strategy of a parasitoid-derived viral gene that has dual functions to manipulate host immunity for a successful parasitism.

A Polydnavirus Protein Tyrosine Phosphatase Negatively Regulates the Host Phenoloxidase Pathway.

Polydnavirus (PDV) is a parasitic factor of endoparasitic wasps and contributes greatly to overcoming the immune response of parasitized hosts. Protein tyrosine phosphatases (PTPs) regulate a wide variety of biological processes at the post-transcriptional level in mammals, but knowledge of PDV PTP action during a parasitoid−host interaction is limited. In this study, we characterized a PTP gene, CvBV_12-6, derived from Cotesia vestalis bracovirus (CvBV), and explored its possible regulatory role in the immune response of the host Plutella xylostella. Our results from qPCR show that CvBV_12-6 was highly expressed in hemocytes at an early stage of parasitization. To explore CvBV_12-6 function, we specifically expressed CvBV_12-6 in Drosophila melanogaster hemocytes. The results show that Hml-Gal4 > CvBV_12-6 suppressed the phenoloxidase activity of hemolymph in D. melanogaster, but exerted no effect on the total count or the viability of the hemocytes. In addition, the Hml-Gal4 > CvBV_12-6 flies exhibited decreased antibacterial abilities against Staphylococcus aureus. Similarly, we found that CvBV_12-6 significantly suppressed the melanization of the host P. xylostella 24 h post parasitization and reduced the viability, but not the number, of hemocytes. In conclusion, CvBV_12-6 negatively regulated both cellular and humoral immunity in P. xylostella, and the related molecular mechanism may be universal to insects.

CLP gene family, a new gene family of Cotesia vestalis bracovirus inhibits melanization of Plutella xylostella hemolymph.

Polydnaviruses (PDVs) are obligatory symbionts of parasitoid wasps and play an important role in suppressing host immune defenses. Although PDV genes that inhibit host melanization are known in Microplitis bracovirus, the functional homologs in Cotesia bracoviruses remain unknown. Here, we find that Cotesia vestalis bracovirus (CvBV) can inhibit hemolymph melanization of its host, Plutella xylostella larvae, during the early stages of parasitization, and that overexpression of highly expressed CvBV genes reduced host phenoloxidase activity. Furthermore, CvBV-7-1 in particular reduced host phenoloxidase activity within 12 h, and the injection of anti-CvBV-7-1 antibody increased the melanization of parasitized host larvae. Further analyses showed that CvBV-7-1 and three homologs from other Cotesia bracoviruses possessed a C-terminal leucine/isoleucine-rich region and had a similar function in inhibiting melanization. Therefore, a new family of bracovirus genes was proposed and named as C-terminal Leucine/isoleucine-rich Protein (CLP). Ectopic expression of CvBV-7-1 in Drosophila hemocytes increased susceptibility to bacterial repression of melanization and reduced the melanotic encapsulation of parasitized D. melanogaster by the parasitoid Leptopilina boulardi. The formation rate of wasp pupae and the eclosion rate of C. vestalis were affected when the function of CvBV-7-1 was blocked. Our findings suggest that CLP genes from Cotesia bracoviruses encoded proteins that contain a C-terminal leucine/isoleucine-rich region and function as melanization inhibitors during the early stage of parasitization, which is important for successful parasitization.

Genome-Wide Profiling of Diadegma semiclausum Ichnovirus Integration in Parasitized Plutella xylostella Hemocytes Identifies Host Integration Motifs and Insertion Sites.

Polydnaviruses (PDVs), classified into two genera, bracoviruses (BVs) and ichnoviruses (IVs), are large, double-stranded DNA viruses, which are beneficial symbionts of parasitoid wasps. PDVs do not replicate in their infected lepidopteran hosts. BV circles have been demonstrated to be integrated into host genomic DNA after natural parasitization. However, the integrations of IV circles in vivo remain largely unknown. Here, we analyzed the integration of Diadegma semiclausum ichnovirus (DsIV) in the genomic DNA of parasitized Plutella xylostella hemocytes. We found that DsIV circles are present in host hemocytes with non-integrated and integrated forms. Moreover, DsIV integrates its DNA circles into the host genome by two distinct strategies, conservatively, and randomly. We also found that four conserved-broken circles share similar motifs containing two reverse complementary repeats at their breaking sites, which were host integration motifs (HIMs). We also predicted HIMs of eight circles from other ichnoviruses, indicating that a HIM-mediated specific mechanism was conserved in IV integrations. Investigation of DsIV circle insertion sites of the host genome revealed the enrichment of microhomologies between the host genome and the DsIV circles at integration breakpoints. These findings will deepen our understanding of the infections of PDVs, especially IVs.

Parasitoid polydnaviruses and immune interaction with secondary hosts.

Polydnaviruses (PDVs) are obligatory symbionts with parasitoid wasps. The PDV virions are produced solely in wasp (the primary host) calyx cells. They are injected into caterpillar hosts (the secondary host) during parasitoid oviposition, where they express irreplaceable actions to ensure survival and development of wasp larvae. Some of PDV gene products suppress host immune responses while others alter host growth, metabolism or endocrine system. Here, we treat new findings on PDV gene products and their action on immunity within secondary hosts.

Laccase 1 gene from Plutella xylostella (PxLac1) and its functions in humoral immune response.

Laccase (EC 1.10.3.2) is a phenoloxidase found in many insect species. The Laccase 1 gene from Plutella xylostella (PxLac1) was cloned, and its expression patterns and functions were determined using qPCR and RNAi methods. The results showed that the expression levels of PxLac1 were consistently high in all larval stages, and the most abundant was in the midgut during the 4th instar stage. Moreover, the expression of PxLac1 was up-regulated in response to bacterial infection, and decreased 24 h after being parasitized by Cotesia vestalis. Further analyses indicated that the effect of parasitization on PxLac1 was induced by active C. vestalis Bracovirus (CvBV). Haemocyte-free hemolymph phenoloxidase (PO) activity was suppressed when PxLac1 was treated with RNAi. Our results provide evidence for a connection between the Laccase 1 gene and insect immunity, and revealed that parasitoid polydnavirus suppresses host PO activity via PxLac1 regulation.