Deacetylation of BmAda3 is required for cell apoptosis caused by Bombyx mori nucleopolyhedrovirus infection

Deacetylation of ACO2 Is Essential for Inhibiting Bombyx mori Nucleopolyhedrovirus Propagation

Bombyx mori nucleopolyhedrovirus (BmNPV) is a specific pathogen of Bombyx mori that can significantly impede agricultural development. Accumulating evidence indicates that the viral proliferation in the host requires an ample supply of energy. However, the correlative reports of baculovirus are deficient, especially on the acetylation modification of tricarboxylic acid cycle (TCA cycle) metabolic enzymes. Our recent quantitative analysis of protein acetylome revealed that mitochondrial aconitase (ACO2) could be modified by (de)acetylation at lysine 56 (K56) during the BmNPV infection; however, the underlying mechanism is yet unknown. In order to understand this regulatory mechanism, the modification site K56 was mutated to arginine (Lys56Arg; K56R) to mimic deacetylated lysine. The results showed that mimic deacetylated mitochondrial ACO2 restricted enzymatic activity. Although the ATP production was enhanced after viral infection, K56 deacetylation of ACO2 suppressed BmN cellular ATP levels and mitochondrial membrane potential by affecting citrate synthase and isocitrate dehydrogenase activities compared with wild-type ACO2. Furthermore, the deacetylation of exogenous ACO2 lowered BmNPV replication and generation of progeny viruses. In summary, our study on ACO2 revealed the potential mechanism underlying WT ACO2 promotes the proliferation of BmNPV and K56 deacetylation of ACO2 eliminates this promotional effect, which might provide novel insights for developing antiviral strategies.

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.

Progress on innate immune evasion and live attenuated vaccine of pseudorabies virus

Pseudorabies virus (PRV) is a highly infectious disease that can infect most mammals, with pigs as the only natural host, has caused considerable economic losses to the pig husbandry of the world. Innate immunity is the first defense line of the host against the attack of pathogens and is essential for the proper establishment of adaptive immunity. The host uses the innate immune response to against the invasion of PRV; however PRV makes use of various strategies to inhibit the innate immunity to promote the virus replication. Currently, live attenuated vaccine is used to prevent pig from infection with the PRV worldwide, such as Bartha K61. However, a growing number of data indicates that these vaccines do not provide complete protection against new PRV variants that have emerged since late 2011. Here we summarized the interactions between PRV and host innate immunity and the current status of live attenuated PRV vaccines to promote the development of novel and more effective PRV vaccines.

Bombyx mori transcription factor, E74A, beneficially affects BmNPV infection through direct interaction

BACKGROUND

Nucleopolyhedrovirus (NPV), one of the baculoviruses, is a promising biopesticide for pest control. Lepidopteran account for 70% of pests, therefore investigation on highly conserved genes associated with viral infections in the lepidopteran model, the silkworm, will serve as a valuable reference for improving the effectiveness of pest management. BmE74A is a member of the erythroblast transformation-specific (ETS) family of transcription factors in Bombyx mori, which we previously found to be highly conserved and closely associated with BmNPV. This study aimed to elucidate the role of BmE74A in viral infection.

RESULTS

A significantly high expression of BmE74A in eggs indicated its important role in embryonic development, as did relatively high expressions in the hemolymph and midgut. Significant differences in BmE74A expression in different resistant strains after BmNPV infection suggested its involvement as a response to viral infection. Moreover, RNA interference (RNAi) and overexpression experiments confirmed the important role of BmE74A in promoting viral infection. BmNPV infection was significantly suppressed and enhanced by BmE74A knockdown and overexpression, respectively. Besides, BmE74A was found to regulate the expression of BmMdm2 and Bmp53. Furthermore, the binding of ETS, the functional domain of BmE74A, to occlusion-derived virus proteins was confirmed by far-western blotting, and four viral proteins that may interact with ETS proteins were identified by mass spectrometry. Similarly, a homolog of BmE74A in Spodoptera litura was also found to be involved in larval susceptibility to BmNPV.

CONCLUSION

BmE74A promotes BmNPV proliferation by directly interacting with the virus, which may be related to the suppression of the p53 pathway. © 2022 Society of Chemical Industry.