Background: Daphnis nerii cypovirus-23 (DnCPV-23) is a new type of cypovirus and has a lethal effect on the oleander hawk moth, Daphnis nerii which feeds on leave of Oleander and Catharanthus et al. After DnCPV-23 infection, the change of Daphnis nerii responses has not been reported. Methods: To better understand the pathogenic mechanism of DnCPV-23 infection, 3rd-instar Daphnis nerii larvae were orally infected with DnCPV-23 occlusion bodies and the transcriptional responses of the Daphnis nerii midgut were analyzed 72 h post-infection using RNA-seq. Results: The results showed that 1979 differentially expressed Daphnis nerii transcripts in the infected midgut had been identified. KEGG analysis showed that protein digestion and absorption, Toll and Imd signaling pathway were down-regulated. Based on the result, we speculated that food digestion and absorption in insect midgut might be impaired after virus infection. In addition, the down-regulation of the immune response may make D. nerii more susceptible to bacterial infections. Glycerophospholipid metabolism and xenobiotics metabolism were up-regulated. These two types of pathways may affect the viral replication and xenobiotic detoxification of insect, respectively. Conclusion: These results may facilitate a better understanding of the changes in Daphnis nerii metabolism during cypovirus infection and serve as a basis for future research on the molecular mechanism of DnCPV-23 invasion.

ER stress occurs in many physiological and pathological conditions. However, how chronic ER stress is alleviated in specific cells in an intact organism is an outstanding question. Here, overexpressing the gap junction protein UNC-9 (Uncoordinated) in C. elegans neurons triggers the Ire1-Xbp1-mediated stress response in an age-dependent and cell-autonomous manner. The p38 MAPK PMK-3 acts upon the phosphorylation of IRE-1 to regulate chronic stress. Overexpressing gap junction protein also activates autophagy and the insulin pathway functions through autophagy, but not the transcription of genes encoding ER chaperones, to counteract the p38-Ire1-Xbp1-mediated stress response. Together, these results reveal an intricate cellular regulatory network in response to chronic stress in a subset of cells in multicellular organism. Author Summary: The accumulation of unfolded proteins triggers the ER stress response (UPR), which allows cells to fight against fluctuations in protein expression under both physiological and pathological conditions. Severe acute ER stress responses can be induced by drug treatment. However, such intense ER stress rarely occurs ubiquitously in every cell type in vivo . Here, we designed a genetic system in the nematode C. elegans , which allows us to induce ER stress in specific cells, without drug treatment or any other external stimuli, and then to monitor the stress response. Using this system, genetic screens identified that the p38 MAPK directly acts through the IRE-1-XBP-1 branch of the UPR to promote the stress response. Meanwhile, the insulin receptor functions through autophagy activation to counteract the p38-IRE-1-XBP-1 pathway. Together, these results reveal an intricate cellular regulatory network in response to chronic stress in multicellular organism.

Daphnis nerii cypovirus-23 (DnCPV-23) is a new type of cypovirus that has a lethal effect on many species of Sphingidae pests. DnCPV-23 can replicate in Spodoptera frugiperda Sf9 cells, but the replication characteristics of the virus in this cell line are still unclear. To determine the replication characteristics of DnCPV-23 in Sf9 cells, uninfected Sf9 cells and Sf9 cells at 24 and 72 h after DnCPV-23 infection were collected for transcriptome analysis. Compared to uninfected Sf9 cells, a total of 188 and 595 differentially expressed genes (DEGs) were identified in Sf9 cells collected at 24 hpi and 72 h, respectively. KEGG analyses revealed that 139 common DEGs in two treatment groups were related to nutrition and energy metabolism-related processes, cell membrane integrity and function-related pathways, detoxification-related pathways, growth and development-related pathways, and so on. We speculated that these cellular processes might be manipulated by viruses to promote replication. This study provides an important basis for further in-depth research on the mechanism of interaction between viruses and hosts. It provides additional basic information for the future exploitation of DnCPV-23 as a biological insecticide.

Daphnis nerii can severely damage pine forests worldwide. Daphnis nerii cypovirus-23 (DnCPV-23) is an important viral pathogen for controlling D. nerii. However, the mechanism underlying DnCPV-23 cell entry has not been elucidated. In this study, we determined that VP3 mediates the binding of DnCPV-23 to host brush border membrane vesicles. Far-Western blotting and mass spectrometry results revealed that a Manduca sexta alpha-glucosidase (MsAGL) can interact with VP3. The interaction between MsAGL and VP3 was verified by co-immunoprecipitation and glutathione S-transferase pull-down assays. Notably, MsAGL influenced DnCPV-23 entry into host cells, including attachment and the subsequent internalization of the virus. Furthermore, MsAGL inhibited DnCPV-23 infections of M. sexta cells and D. nerii larvae. In summary, we confirmed that VP3 of DnCPV-23 mediates cell entry, while also identifying MsAGL as an entry factor for DnCPV-23. The study findings provide useful insights relevant for further elucidating the cell entry mechanisms of cypoviruses.