The BIR and BIR-like domains of Bombyx mori nucleopolyhedrovirus IAP2 protein are required for efficient viral propagation

Evaluation of Insecticidal activity and Genetic Expressions of some Essential Oil and Methomyl Lannate 90% against Spodoptera frugiperda [J.E. Smith]; (Lepidoptera: Noctuidae).. [DOI: 10.21203/rs.3.rs-3156489/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0]

Fall Armyworm (FAW) Spodoptera frugiperda [J.E. Smith] (Lepidoptera: Noctuidae) is regarded as a major pest of various economic crops, their caterpillars are a highly destructive and have a wide host range. This study's goal was to assess the insecticide potency of essential oils [rosemary (Rosmarinus officinalis L.), lemongrass (Cymbopogon citratus) and Cinnamon (Cinnamomum zeylanicum)] and Methomyl Lannate 90% commerial Insecticide to control FAW and their effected on Expression of caspase-8 and Inhibitor of Apoptosis Protein (IAP) genes and Expression of Acetylcholinesterase (AChE) gene in FAW. The insecticidal activity against 2nd larval instar was evaluated with five concentrations (2.5%, 2%, 1.0%, 0.5% and 0.25%) for essential oil and four concentrations 0.4%, 0.2%,0.15% and 0.05% for Methomyl Lannate 90%. The findings indicated that raising both essential oil concentrations and Methomyl Lannate 90%, resulted in increased the larval mortality at high concentration. Lemongrass and Cinnamon oil produced about to the same estimated LC50, whereas Methomyl Lannate 90% was (0.3%). Cymbopogon citratus (1.68%) had higher Caspase-8 gene expression levels compared to the control, but at a lower level than Rosmarinus officinalis L. (2.59%) and Cinnamomum zeylanicum (1.67%). The expression levels of Ache gene in the treated by low concentration of Methomyl Lannate were increased (by 313%) significant compared with the control but without significant differences. FAW death as a result of treatment with the tested oils having an effect on the genes that the pest uses to express critical processes. As a result, using the tested essential oils as a substitute for conventional management of FAW is a brilliance option.

Transcriptome analysis reveals that knocking out BmNPV iap2 induces apoptosis by inhibiting the oxidative phosphorylation pathway

Apoptosis is essential for the normal growth, development, and immunity defense of living organisms, and its function and mechanisms have been intensively studied. When viral infection occurs, apoptosis is triggered, causing programmed death of the infected cells. Meanwhile, viruses have also evolved countermeasures to inhibit apoptosis in host cells. We previously constructed a transgenic silkworm line with significantly improved resistance to Bombyx mori nucleopolyhedrovirus (BmNPV) by knocking out the BmNPV inhibitor of apoptosis 2 (iap2) gene. However, the mechanism of how IAP2 induces apoptosis still needs to be further investigated. Here, the transcriptomes of Cas9(-)/sgiap2 (-) and Cas9(+)/sgiap2(+) strains were analyzed at 48 h after BmNPV infection, and a total of 709 differential genes were obtained. A KEGG analysis revealed that the differentially expressed genes were enriched in the oxidative phosphorylation, proteasome, and ribosome pathways. In the oxidative phosphorylation pathway, 41 differentially expressed genes were downregulated, and 12 of these genes were verified by qRT-PCR. More importantly, the knockout of BmNPV iap2 led to the inhibition of the oxidative phosphorylation pathway, followed by activated oxidative stress triggered apoptosis, thereby inhibiting the replication of BmNPV in vitro and vivo. The results provide a basis for the analysis of the initiation of apoptosis that can inhibit virus proliferation, and the study presents new ideas for the subsequent creation of resistant material.

Functional analyses of inhibitor of apoptosis protein 1 (IAP1) of Antheraea pernyi multinucleocapsid nucleopolyhedrovirus (AnpeNPV) in viral replication and occlusion body production

Inhibitor of apoptosis protein 1 (IAP1) of Antheraea pernyi multinucleocapsid nucleopolyhedrovirus (AnpeNPV) belongs to the baculovirus IAP1 type. The function of AnpeNPV-IAP1 in viral replication and occlusion body (OB) production remains unknown. In this study, we demonstrated that AnpeNPV-iap1 is a late gene. AnpeNPV-IAP1 mainly localizes to the nuclear ring zone and exhibits dynamic distribution in the cytoplasm and the virogenic stroma during AnpeNPV infection. AnpeNPV-IAP1 impacted the expression of a variety of viral genes at the very late phase of infection in Tn-Hi5 cells. The deletion of AnpeNPV-iap1 caused decreased expression levels of polyhedrin, morphological changes to OBs and reduced OB production in A. pernyi pupae, along with a lengthening of the lethal time of A. pernyi larvae. These results suggest that AnpeNPV-iap1 is involved in regulating viral gene expression, OB production and morphogenesis in A. pernyi.

Impact of Group II Baculovirus IAPs on Virus-Induced Apoptosis in Insect Cells

Apoptosis plays an important role in virus-host interactions and is a major element of the insect immune response. Exploring the regulatory mechanisms of virus-induced apoptosis through the expression of apoptotic genes holds important research and application value. Functional research on the reported inhibitor of apoptosis proteins (IAPs) mainly focuses on the group I baculovirus, while the functions of the group II baculovirus IAPs remains unclear. To explore its role in the regulation of the apoptosis of insect cells, we constructed the transient expression vector (pIE1 vectors) and the recombinant baculovirus expressing Bsiap genes (from the Buzura suppressaria nucleopolyhedrovirus) of the group II baculovirus. Apoptosis gene expression results and the virus-induced apoptosis rate show that the overexpression of BsIAP1 could promote apoptosis in insect cells. However, the overexpression of BsIAP2 and BsIAP3 decreases the expression of apoptotic genes, revealing an inhibitory effect. Results on the impact of baculovirus-induced apoptosis also confirm that BsIAP1 reduces viral nucleocapsid expression and the baculovirus titer, while BsIAP2 and BsIAP3 increase them significantly. Furthermore, compared with single expression, the co-expression of BsIAP2 and BsIAP3 significantly reduces the rate of virus-induced apoptosis and improves the expression of nucleocapsids and the titer of offspring virus, indicating the synergistic effect on BsIAP2 and BsIAP3. In addition, combined expression of all three BsIAPs significantly reduced levels of intracellular apoptosis-related genes (including apoptosis and anti-apoptosis genes), as well as apoptosis rate and progeny virus titer, indicating that life activities in insect cells are also inhibited. These findings reveal the relationship between apoptosis and group II baculovirus IAP, which provide an experimental and theoretical basis for further exploration of the molecular mechanism between group II baculoviruses and insect cells.

Gene editing the BmNPV inhibitor of apoptosis protein 2 (iap2) as an antiviral strategy in transgenic silkworm

Apoptosis is a cellular defense mechanism used for the elimination of host cells infected by viruses. Viruses have evolved corresponding inhibitors of apoptosis genes to promote their replication. Anti-apoptosis-related genes, involved in baculovirus proliferation, have been proposed but it is unclear whether these genes can be manipulated in gene therapy. We constructed a transgenic silkworm, using the CRISPR/Cas9 system to knock out the BmNPV inhibitor of apoptosis 2 (iap2). The sequencing results showed that all the sequences could edit the target site of BmNPV iap2 gene. There were no differences in economic traits and growth tests between the BmNPV iap2 knockout strain transgenic silkworm lines and the control groups. However, the mortality rate was significantly reduced, the median lethal dose (LD50) was about 100 times higher than the control group, and the onset time was prolonged by 1-2 days after knocking out BmNPV iap2. In addition, the expression levels of apoptotic-related genes Bmiap2, BmICE and BmDreed were significantly affected and the activity of caspase 9 was increased after BmNPV iap2 being edited in transgenic silkworm. These results demonstrated that gene editing BmNPV iap2 could significantly inhibit BmNPV replication and proliferation. This approach provides a new strategy for antiviral research.

Evolutionary and functional analyses of the interaction between the Bombyx mori inhibitor of apoptosis (IAP) and nucleopolyhedrovirus IAPs

As an important insect immune response, apoptosis plays a critical role in the interaction between baculoviruses and insect hosts. Previous reports have identified inhibitor of apoptosis (IAP) proteins in both insects and baculoviruses, but the relationship between these proteins is still not clearly understood. Here, we found that insect IAP proteins were clustered with baculovirus IAP3, suggesting that the baculovirus iap3 gene might be derived from the Lepidoptera or Diptera. We demonstrated that Bombyx mori inhibitor of apoptosis (Bmiap) gene had an inhibitory effect on apoptosis in silkworm cells. Further analysis of the effects of Bmiap genes on the proliferation of B. mori nucleopolyhedrovirus (BmNPV) showed that both the Bmiap and BmNPV iap genes increased BmNPV proliferation after BmNPV infected silkworm cells. Our results also indicated that BmNPV IAP1 and IAP2 directly interacted with BmIAP in silkworm cells, implying that the Bmiap gene might be hijacked by BmNPV iap genes during BmNPV infection. Taken together, our results provide important insights into the functional relationships of iap genes, and improve our knowledge of apoptosis in baculoviruses and insect hosts.

Pro-Apoptotic Function Analysis of the Reaper Homologue IBM1 in Spodoptera frugiperda

As an important type of programmed cell death, apoptosis plays a critical role in lepidopteran insects in response to various internal and external stresses. It is controlled by a network of genes such as those encoding the inhibitor of apoptosis proteins. However, there are few studies on apoptosis-related genes in Spodoptera frugiperda. In this study, an orthologue to the Drosophila reaper gene, named Sf-IBM1, was identified from S. frugiperda, and a full-length sequence was obtained by reverse transcription polymerase chain reaction (RT-PCR) and rapid amplification of cDNA ends PCR (RACE-PCR). The expression pattern of Sf-IBM1 was determined in different developmental stages and various tissues. Apoptotic stimuli including azadirachtin, camptothecin, and ultraviolet radiation (UV) induced the expression of Sf-IBM1 at both transcript and protein levels. Overexpression of Sf-IBM1 induced apoptosis in Sf9 cells, and the Sf-IBM1 protein was localized in mitochondria. The apoptosis induced by Sf-IBM1 could be blocked by the caspase universal inhibitor carbobenzoxy-valyl-alanyl-aspartyl-[O-methyl]-fluoromethylketone (Z-VAD-FMK) and Sf-IAP1. Our results provide valuable information that should contribute to a better understanding of the molecular events that lead to apoptosis in lepidopterans.

Antiviral immune responses of Bombyx mori cells during abortive infection with Autographa californica multiple nucleopolyhedrovirus

Lepidopteran cells rely on multiple antiviral responses to defend against baculovirus infections, including apoptosis, global protein synthesis shutdown, and rRNA degradation. Here, we characterized apoptosis and rRNA degradation in Autographa californica multiple nucleopolyhedrovirus (AcMNPV)-infected Bombyx mori cells, a system resulting in abortive infection, in relation to viral DNA replication and viral late gene expression. RNAi-mediated silencing of viral DNA replication-related genes prevented apoptosis, but not rRNA degradation, in B. mori cells infected with p35-deficient AcMNPV. Additionally, AcMNPV, but not B. mori nucleopolyhedrovirus (BmNPV), drastically reduced B. mori cellular iap1 transcript levels and p35-deficient AcMNPV induced more prominent apoptosis than did p35-deficient BmNPV. These results, together with previous results that global protein synthesis shutdown follows viral DNA replication, demonstrate that rRNA degradation is the primary antiviral response that abolishes productive AcMNPV infection of B. mori cells. Our results also demonstrate that B. mori cells induce apoptosis to a different extent depending on NPV species.

Function analysis and application of IAP1/2 of Autographa californica multiple nucleopolyhedrovirus

We confirmed the function of Ac-IAPs and developed a useful AcMNPV-iap2-egfp, which provided theoretical foundation for using and modifying AcMNPV.

MERS coronavirus induces apoptosis in kidney and lung by upregulating Smad7 and FGF2

Middle East respiratory syndrome coronavirus (MERS-CoV) causes sporadic zoonotic disease and healthcare-associated outbreaks in human. MERS is often complicated by acute respiratory distress syndrome (ARDS) and multi-organ failure^1,2. The high incidence of renal failure in MERS is a unique clinical feature not often found in other human coronavirus infections^3,4. Whether MERS-CoV infects the kidney and how it triggers renal failure are not understood^5,6. Here, we demonstrated renal infection and apoptotic induction by MERS-CoV in human ex vivo organ culture and a nonhuman primate model. High-throughput analysis revealed that the cellular genes most significantly perturbed by MERS-CoV have previously been implicated in renal diseases. Furthermore, MERS-CoV induced apoptosis through upregulation of Smad7 and fibroblast growth factor 2 (FGF2) expression in both kidney and lung cells. Conversely, knockdown of Smad7 effectively inhibited MERS-CoV replication and protected cells from virus-induced cytopathic effects. We further demonstrated that hyperexpression of Smad7 or FGF2 induced a strong apoptotic response in kidney cells. Common marmosets infected by MERS-CoV developed ARDS and disseminated infection in kidneys and other organs. Smad7 and FGF2 expression were elevated in the lungs and kidneys of the infected animals. Our results provide insights into the pathogenesis of MERS-CoV and host targets for treatment.

Renal infection with Middle East respiratory syndrome coronavirus (MERS-CoV) leads to both the induction of apoptosis through upregulation of Smad7 and FGF2 and to renal failure.