Drosophila miR-956 suppression modulates Ectoderm-expressed 4 and inhibits viral replication

MicroRNA bmo-miR-31-5p inhibits apoptosis and promotes BmNPV proliferation by targeting the CYP9e2 gene of Bombyx mori

BACKGROUND

Bombyx mori nuclear polyhedrosis virus (BmNPV), as a typical baculovirus, is the primary pathogen that infects the silkworm B. mori, a lepidopteran species. Owing to the high biological safety of BmNPV in infecting insects, it is commonly utilized as a biological insecticide for pest control. Apoptosis is important in the interaction between the host and pathogenic microorganisms. MicroRNAs (miRNAs) influence immune responses and promote stability of the immune system via apoptosis. Therefore, the study of apoptosis-related miRNA in silkworms during virus infection can not only provide support for standardizing the prevention and control of diseases and insect pests, but also reduce the economic losses to sericulture caused by the misuse of biological pesticides.

RESULTS

Through transcriptome sequencing, we identified a miRNA, miR-31-5p, and demonstrated that it can inhibit apoptosis in silkworm cells and promote the proliferation of BmNPV in BmE-SWU1 cells. We identified a target gene of miR-31-5p, B. mori cytochrome P450 9e2 (BmCYP9e2), and demonstrated that it can promote apoptosis in silkworm cells and inhibit the proliferation of BmNPV. Moreover, we constructed transgenic silkworm strains with miR-31-5p knockout and confirmed that they can inhibit the proliferation of BmNPV.

CONCLUSION

These data indicate that miR-31-5p may exert functions of inhibiting apoptosis and promoting virus proliferation by regulating BmCYP9e2. The findings demonstrate how miRNAs influence host cell apoptosis and how they are involved in the host immune system response to viruses, providing important insights into the applications of biological insecticides for pest control. © 2024 Society of Chemical Industry.

The accumulation of modular serine protease mediated by a novel circRNA sponging miRNA increases Aedes aegypti immunity to fungus

BACKGROUND

Mosquitoes transmit many infectious diseases that affect human health. The fungus Beauveria bassiana is a biological pesticide that is pathogenic to mosquitoes but harmless to the environment.

RESULTS

We found a microRNA (miRNA) that can modulate the antifungal immunity of Aedes aegypti by inhibiting its cognate serine protease. Fungal infection can induce the expression of modular serine protease (ModSP), and ModSP knockdown mosquitoes were more sensitive to B. bassiana infection. The novel miRNA-novel-53 is linked to antifungal immune response and was greatly diminished in infected mosquitoes. The miRNA-novel-53 could bind to the coding sequences of ModSP and impede its expression. Double fluorescence in situ hybridization (FISH) showed that this inhibition occurred in the cytoplasm. The amount of miRNA-novel-53 increased after miRNA agomir injection. This resulted in a significant decrease in ModSP transcript and a significant increase in mortality after fungal infection. An opposite effect was produced after antagomir injection. The miRNA-novel-53 was also knocked out using CRISPR-Cas9, which increased mosquito resistance to the fungus B. bassiana. Moreover, mosquito novel-circ-930 can affect ModSP mRNA by interacting with miRNA-novel-53 during transfection with siRNA or overexpression plasmid.

CONCLUSIONS

Novel-circ-930 affects the expression level of ModSP by a novel-circ-930/miRNA-novel-53/ModSP mechanism to modulate antifungal immunity, revealing new information on innate immunity in insects.

microRNA Expression Dynamics in Culicoides sonorensis Biting Midges Following Blood-Feeding

Culicoides sonorensis midges vector multiple livestock arboviruses, resulting in significant economic losses worldwide. Due to the tight association between virus transmission, blood feeding, and egg development, understanding midge physiology is paramount to limiting pathogen transmission. Previous studies have demonstrated the importance of small non-coding RNAs (ncRNAs), specifically microRNAs (miRNAs), in multiple aspects of vector physiology. These small ncRNAs regulate gene expression at the post-transcriptional level and display differential expression during pathogen infection. Due to the lack of annotated miRNAs in the biting midge and associated expression profiles, we used small RNA-Seq and miRDeep2 analyses to determine the Culicoides miRNAs in whole females and midgut tissues in response to blood feeding. Our analyses revealed 76 miRNAs within C. sonorensis composed of 73 orthologous and three candidate novel miRNAs, as well as conserved miRNA clusters. miRNA conservation suggests an interesting evolutionary relationship between miRNA expression and hematophagy in the infraorder Culicomorpha. We also identified multiple blood meal-regulated and tissue-enriched miRNAs. Lastly, we further identified miRNAs with expression patterns potentially associated with virus infection by probing publicly available datasets. Together, our data provide a foundation for future ncRNA work to untangle the dynamics of gene regulation associated with midge physiology.

Drosophila Ectoderm-expressed 4 modulates JAK/STAT pathway and protects flies against Drosophila C virus infection

Sterile alpha and HEAT/Armadillo motif-containing protein (SARM) is conserved in evolution and negatively regulates TRIF-dependent Toll signaling in mammals. The SARM protein from Litopenaeus vannamei and its Drosophila orthologue Ectoderm-expressed (Ect4) are also involved in immune defense against pathogen infection. However, the functional mechanism of the protective effect remains unclear. In this study, we show that Ect4 is essential for the viral load in flies after a Drosophila C virus (DCV) infection. Viral load is increased in Ect4 mutants resulting in higher mortality rates than wild-type. Overexpression of Ect4 leads to a suppression of virus replication and thus improves the survival rate of the animals. Ect4 is required for the viral induction of STAT-responsive genes, TotA and TotM. Furthermore, Ect4 interacts with Stat92E, affecting the tyrosine phosphorylation and nuclear translocation of Stat92E in S2 cells. Altogether, our study identifies the adaptor protein Ect4 of the Toll pathway contributes to resistance to viral infection and regulates JAK/STAT signaling pathway.

MicroRNAs reshape the immunity of insects in response to bacterial infection

The interaction between bacteria and insects can significantly impact a wide range of different areas because bacteria and insects are widely distributed around the globe. The bacterial-insect interactions have the potential to directly affect human health since insects are vectors for disease transmission, and their interactions can also have economic consequences. In addition, they have been linked to high mortality rates in economically important insects, resulting in substantial economic losses. MicroRNAs (miRNAs) are types of non-coding RNAs involved in regulating gene expression post-transcriptionally. The length of miRNAs ranges from 19 to 22 nucleotides. MiRNAs, in addition to their ability to exhibit dynamic expression patterns, have a diverse range of targets. This enables them to govern various physiological activities in insects, like innate immune responses. Increasing evidence suggests that miRNAs have a crucial biological role in bacterial infection by influencing immune responses and other mechanisms for resistance. This review focuses on some of the most recent and exciting discoveries made in recent years, including the correlation between the dysregulation of miRNA expression in the context of bacterial infection and the progression of the infection. Furthermore, it describes how they profoundly impact the immune responses of the host by targeting the Toll, IMD, and JNK signaling pathways. It also emphasizes the biological function of miRNAs in regulating immune responses in insects. Finally, it also discusses current knowledge gaps about the function of miRNAs in insect immunity, in addition to areas that require more research in the future.

The role of micro RNAs (miRNAs) in the regulation of Drosophila melanogaster's innate immunity

MicroRNAs (miRNAs) are a class of small non-coding RNAs ~19-22 nt long which post-transcriptionally regulate gene expression. Their ability to exhibit dynamic expression patterns coupled with their wide variety of targets allows miRNAs to regulate many processes, including the innate immune response of Drosophila melanogaster. Recent studies have identified miRNAs in Drosophila which are differentially expressed during infection with different pathogens as well as miRNAs that may affect immune signalling when differentially expressed. This review provides an overview of miRNAswhich have been identified to play a role in the immune response of Drosophila through targeting of the Toll and IMD signalling pathways and other immune processes. It will also explore the role of miRNAs in fine-tuning the immune response in Drosophila and highlight current gaps in knowledge regarding the role of miRNAs in immunity and areas for further research.

microRNA-34-5p encoded by Spodoptera frugiperda regulates the replication and infection of Autographa californica multiple nucleopolyhedrovirus by targeting odv-e66, ac78 and ie2

BACKGROUND

Spodoptera frugiperda is one of the significant migratory pests in the Global Alert issued by the Food and Agriculture Organization of the United Nations. As an insect-specific microbial insecticide, baculovirus has been used to control various pests. MicroRNA-34-5p (miR-34-5p) is involved in regulating growth, reproduction and innate immunity to pathogens in insects, playing an essential role in host-virus interactions. In this study, we explored the critical function of miR-34-5p encoded by S. frugiperda in the anti-Autographa californica multiple nucleopolyhedrovirus (AcMNPV), providing a reference for the design of a miR-34-5p target biopesticide against S. frugiperda and a theoretical basis for the wide application of microRNAs (miRNAs) in green pest control technology.

RESULTS

We focused on miR-34-5p identified as downregulated in Sf9 cells and S. frugiperda larvae infected by AcMNPV. The regulatory function of miR-34-5p in AcMNPV-S. frugiperda interactions was studied by transfecting synthetic mimics and inhibitors, and constructing recombinant bacmids with miR-34-5p overexpression. miR-34-5p inhibited the production of infectious budded virions at the cellular and insect levels, inhibited the replication of the viral DNA and glucose metabolism, and increased the transcription of the antimicrobial peptide gloverin. Furthermore, the virus genes odv-e66, ac78 and ie2 were shown to be direct targets.

CONCLUSION

We systematically revealed the mechanism by which miR-34-5p is involved in the insect antiviral process. miR-34-5p inhibited the replication and infection of AcMNPV by directly targeting AcMNPV genes, especially ac78 and ie2. Our study provides a new direction and thinking for the prevention and green control of lepidopteran pests. © 2022 Society of Chemical Industry.

The small RNA landscape is stable with age and resistant to loss of dFOXO signaling in Drosophila

Aging can be defined as the progressive loss of physiological homeostasis that leads to a decline in cellular and organismal function. In recent years, it has become clear that small RNA pathways play a role in aging and aging related phenotypes. Small RNA pathways regulate many important processes including development, cellular physiology, and innate immunity. The pathways illicit a form of posttranscriptional gene regulation that relies on small RNAs bound by the protein components of the RNA-induced silencing complexes (RISCs), which inhibit the expression of complementary RNAs. In Drosophila melanogaster, Argonaute 1 (Ago1) is the core RISC component in microRNA (miRNA) silencing, while Argonaute 2 (Ago2) is the core RISC component in small interfering RNA (siRNA) silencing. The expression of Ago1 and Ago2 is regulated by stress response transcription factor Forkhead box O (dFOXO) increasing siRNA silencing efficiency. dFOXO plays a role in multiple stress responses and regulates pathways important for longevity. Here we use a next-generation sequencing approach to determine the effects of aging on small RNA abundance and RISC loading in male and female Drosophila. In addition, we examine the impact of the loss of dFOXO on these processes. We find that the relative abundance of the majority of small RNAs does not change with age. Additionally, under normal growth conditions, the loss of dFOXO has little effect on the small RNA landscape. However, we observed that age affects loading into RISC for a small number of miRNAs.

Profiling ATM regulated genes in Drosophila at physiological condition and after ionizing radiation

Background

ATM (ataxia-telangiectasia mutated) protein kinase is highly conserved in metazoan, and plays a critical role at DNA damage response, oxidative stress, metabolic stress, immunity, RNA biogenesis etc. Systemic profiling of ATM regulated genes, including protein-coding genes, miRNAs, and long non-coding RNAs, will greatly improve our understanding of ATM functions and its regulation. 

Results

1) differentially expressed protein-coding genes, miRNAs, and long non-coding RNAs in atm mutated flies were identified at physiological condition and after X-ray irradiation. 2) functions of differentially expressed genes in atm mutated flies, regardless of protein-coding genes or non-coding RNAs, are closely related with metabolic process, immune response, DNA damage response or oxidative stress. 3) these phenomena are persistent after irradiation. 4) there is a cross-talk regulation towards miRNAs by ATM, E2f1, and p53 during development and after irradiation. 5) knock-out flies or knock-down flies of most irradiation-induced miRNAs were sensitive to ionizing radiation.

Conclusions

We provide a valuable resource of protein-coding genes, miRNAs, and long non-coding RNAs, for understanding ATM functions and regulations. Our work provides the new evidence of inter-dependence among ATM-E2F1-p53 for the regulation of miRNAs.

Supplementary Information

The online version contains supplementary material available at 10.1186/s41065-022-00254-9.

The developmentally dynamic microRNA transcriptome of Glossina pallidipes tsetse flies, vectors of animal trypanosomiasis

Summary

MicroRNAs (miRNAs) are single stranded gene regulators of 18-25 bp in length. They play a crucial role in regulating several biological processes in insects. However, the functions of miRNA in Glossina pallidipes, one of the biological vectors of African animal trypanosomosis in sub-Saharan Africa, remain poorly characterized. We used a combination of both molecular biology and bioinformatics techniques to identify miRNA genes at different developmental stages (larvae, pupae, teneral and reproductive unmated adults, gravid females) and sexes of G. pallidipes. We identified 157 mature miRNA genes, including 12 novel miRNAs unique to G. pallidipes. Moreover, we identified 93 miRNA genes that were differentially expressed by sex and/or in specific developmental stages. By combining both miRanda and RNAhybrid algorithms, we identified 5550 of their target genes. Further analyses with the Gene Ontology term and KEGG pathways for these predicted target genes suggested that the miRNAs may be involved in key developmental biological processes. Our results provide the first repository of G. pallidipes miRNAs across developmental stages, some of which appear to play crucial roles in tsetse fly development. Hence, our findings provide a better understanding of tsetse biology and a baseline for exploring miRNA genes in tsetse flies.

Availability and implementation

Raw sequence data are available from NCBI Sequence Read Archives (SRA) under Bioproject accession number PRJNA590626.

Supplementary information

Supplementary data are available at Bioinformatics Advances online.

Sensing and signalling viral infection in drosophila

The fruitfly Drosophila melanogaster is a valuable model to unravel mechanisms of innate immunity, in particular in the context of viral infections. RNA interference, and more specifically the small interfering RNA pathway, is a major component of antiviral immunity in drosophila. In addition, the contribution of inducible transcriptional responses to the control of viruses in drosophila and other invertebrates is increasingly recognized. In particular, the recent discovery of a STING-IKKβ-Relish signalling cassette in drosophila has confirmed that NF-κB transcription factors play an important role in the control of viral infections, in addition to bacterial and fungal infections. Here, we review recent developments in the field, which begin to shed light on the mechanisms involved in sensing of viral infections and in signalling leading to production of antiviral effectors.

The Interplay Between Viruses and RNAi Pathways in Insects

As an overarching immune mechanism, RNA interference (RNAi) displays pathogen specificity and memory via different pathways. The small interfering RNA (siRNA) pathway is the primary antiviral defense mechanism against RNA viruses of insects and plays a lesser role in defense against DNA viruses. Reflecting the pivotal role of the siRNA pathway in virus selection, different virus families have independently evolved unique strategies to counter this host response, including protein-mediated, decoy RNA-based, and microRNA-based strategies. In this review, we outline the interplay between insect viruses and the different pathways of the RNAi antiviral response; describe practical application of these interactions for improved expression systems and for pest and disease management; and highlight research avenues for advancement of the field.

Global Analysis of Small Non-Coding RNA Populations across Tissues in the Malaria Vector, Anopheles gambiae

Malaria is a major global health problem, where the anautogenous female mosquito Anopheles gambiae serves as a major vector. In order to combat this devastating disease, understanding mosquito physiology is paramount. Numerous studies in the vector field demonstrate that small non-coding RNAs (ncRNAs) play essential roles in numerous aspects of mosquito physiology. While our previous miRNA annotation work demonstrated expression dynamics across differing tissues, miRNAs represented less than 20% of all small ncRNAs in our small RNA-Seq libraries. To this end, we systematically classified multiple small ncRNA groups across mosquito tissues. Here we (i) determined a new enriched-midgut miRNA, (ii) updated the piRNA annotation in ovaries with a genomic map of unique-mapping piRNAs, (iii) identified pan-tissue and tissue-enriched mRNA-derived small ncRNAs, and (iv) assessed AGO1- and AGO2- loading of candidate small ncRNAs. Continued research will broaden our view of small ncRNAs and greatly aide in our understanding on how these molecules contribute to mosquito physiology.

JNK pathway plays a key role in the immune system of the pea aphid and is regulated by microRNA-184

Different from holometabolous insects, the hemipteran species such as pea aphid Acyrthosiphon pisum exhibit reduced immune responses with the absence of the genes coding for antimicrobial peptide (AMP), immune deficiency (IMD), peptidoglycan recognition proteins (PGRPs), and other immune-related molecules. Prior studies have proved that phenoloxidase (PO)-mediated melanization, hemocyte-mediated phagocytosis, and reactive oxygen species (ROS) participate in pea aphid defense against bacterial infection. Also, the conserved signaling, Jun N-terminal kinase (JNK) pathway, has been suggested to be involved in pea aphid immune defense. However, the precise role of the JNK signaling, its interplay with other immune responses and its regulation in pea aphid are largely unknown. In this study, using in vitro biochemical assays and in vivo bioassays, we demonstrated that the JNK pathway regulated hemolymph PO activity, hydrogen peroxide concentration and hemocyte phagocytosis in bacteria infected pea aphids, suggesting that the JNK pathway plays a central role in regulating immune responses in pea aphid. We further revealed the JNK pathway is regulated by microRNA-184 in response to bacterial infection. It is possible that in common the JNK pathway plays a key role in immune system of hemipteran insects and microRNA-184 regulates the JNK pathway in animals.

Tenth Scientific Biennial Meeting of the Australasian Virology Society-AVS10 2019

The Australasian Virology Society (AVS) aims to promote, support and advocate for the discipline of virology in the Australasian region. The society was incorporated in 2011 after 10 years operating as the Australian Virology Group (AVG) founded in 2001, coinciding with the inaugural biennial scientific meeting. AVS conferences aim to provide a forum for the dissemination of all aspects of virology, foster collaboration, and encourage participation by students and post-doctoral researchers. The tenth Australasian Virology Society (AVS10) scientific meeting was held on 2–5 December 2019 in Queenstown, New Zealand. This report highlights the latest research presented at the meeting, which included cutting-edge virology presented by our international plenary speakers Ana Fernandez-Sesma and Benjamin tenOever, and keynote Richard Kuhn. AVS10 honoured female pioneers in Australian virology, Lorena Brown and Barbara Coulson. We report outcomes from the AVS10 career development session on “Successfully transitioning from post-doc to lab head”, winners of best presentation awards, and the AVS gender equity policy, initiated in 2013. Plans for the 2021 meeting are underway which will celebrate the 20th anniversary of AVS where it all began, in Fraser Island, Queensland, Australia.

Viral and subviral derived small RNAs as pathogenic determinants in plants and insects

The phenotypic manifestations of disease induced by viruses and subviral infectious entities are the result of complex molecular interactions between host and viral factors. The viral determinants of the diseased phenotype have traditionally been sought at the level of structural or non-structural proteins. However, the discovery of RNA silencing mechanisms has led to speculations that determinants of the diseased phenotype are caused by viral nucleic acid sequences in addition to proteins. RNA silencing is a gene regulation mechanism conserved within eukaryotic kingdoms (with the exception of some yeast species), and in plants and insects it also functions as an antiviral mechanism. Non-coding RNAs of viral origin, ranging in size from 21 to 24 nucleotides (viral small interfering RNAs, vsiRNAs) accumulate in virus-infected tissues and organs, in some cases to comparable levels as the entire complement of host-encoded small interfering RNAs. Upon incorporation into RNA-induced silencing complexes, vsiRNAs can mediate cleavage or induce translational inhibition of nucleic acid targets in a sequence-specific manner. This review focuses on recent findings that suggest an increased complexity of small RNA-based interactions between virus and host. We mainly address plant viruses, but where applicable discuss insect viruses as well. Prominence is given to studies that have indisputably demonstrated that vsiRNAs determine diseased phenotype by either carrying sequence determinants or, indirectly, by altering host-gene regulatory pathways. Results from these studies suggest biotechnological applications, which are also discussed.

Viral suppressors of RNAi employ a rapid screening mode to discriminate viral RNA from cellular small RNA

RNA interference (RNAi) is an indispensable mechanism for antiviral defense in insects, including mosquitoes that transmit human diseases. To escape this antiviral defense system, viruses encode suppressors of RNAi that prevent elimination of viral RNAs, and thus ensure efficient virus accumulation. Although the first animal Viral Suppressor of RNAi (VSR) was identified more than a decade ago, the molecular basis of RNAi suppression by these viral proteins remains unclear. Here, we developed a single-molecule fluorescence assay to investigate how VSRs inhibit the recognition of viral RNAs by Dcr-2, a key endoribonuclease enzyme in the RNAi pathway. Using VSRs from three insect RNA viruses (Culex Y virus, Drosophila X virus and Drosophila C virus), we reveal bimodal physical interactions between RNA molecules and VSRs. During initial interactions, these VSRs rapidly discriminate short RNA substrates from long dsRNA. VSRs engage nearly irreversible binding with long dsRNAs, thereby shielding it from recognition by Dcr-2. We propose that the length-dependent switch from rapid screening to irreversible binding reflects the main mechanism by which VSRs distinguish viral dsRNA from cellular RNA species such as microRNAs.

SARM: From immune regulator to cell executioner

SARM is the fifth and most conserved member of the Toll/Il-1 Receptor (TIR) adaptor family. However, unlike the other TIR adaptors, MyD88, Mal, TRIF and TRAM, SARM does not participate in transducing signals downstream of TLRs. By contrast SARM inhibits TLR signalling by interacting with the adaptors TRIF and MyD88. In addition, SARM also has positive roles in innate immunity by activating specific transcriptional programs following immune challenge. SARM has a pivotal role in activating different forms of cell death following cellular stress and viral infection. Many of these functions of mammalian SARM are also reflected in SARM orthologues in lower organisms such as C. elegans and Drosophila. SARM expression is particularly enriched in neurons of the CNS and SARM has a critical role in neuronal death and in axon degeneration. Recent fascinating molecular insights have been revealed as to the molecular mechanism of SARM mediated axon degeneration. SARM has been shown to deplete NAD+ by possessing intrinsic NADase activity in the TIR domain of the protein. This activity can be activated experimentally by forced dimerization of the TIR domain. It is thought that this activity of SARM is normally switched off by the axo-protective activities of NMNAT2 which maintain low levels of the NAD+ precursor NMN. Therefore, there is now great excitement in the field of SARM research as targeting this enzymatic activity of SARM may lead to the development of new therapies for neurodegenerative diseases such as multiple sclerosis and motor neuron disease.

miRNAs in Insects Infected by Animal and Plant Viruses

Viruses vectored by insects cause severe medical and agricultural burdens. The process of virus infection of insects regulates and is regulated by a complex interplay of biomolecules including the small, non-coding microRNAs (miRNAs). Considered an anomaly upon its discovery only around 25 years ago, miRNAs as a class have challenged the molecular central dogma which essentially typifies RNAs as just intermediaries in the flow of information from DNA to protein. miRNAs are now known to be common modulators or fine-tuners of gene expression. While recent years has seen an increased emphasis on understanding the role of miRNAs in host-virus associations, existing literature on the interaction between insects and their arthropod-borne viruses (arboviruses) is largely restricted to miRNA abundance profiling. Here we analyse the commonalities and contrasts between miRNA abundance profiles with different host-arbovirus combinations and outline a suggested pipeline and criteria for functional analysis of the contribution of miRNAs to the insect vector-virus interaction. Finally, we discuss the potential use of the model organism, Drosophila melanogaster, in complementing research on the role of miRNAs in insect vector-virus interaction.