Insect-resistant Mechanism of Recombinant Baculovirus AcMNPV-PK2-EGFP against Spodoptera exigua Larvae

Autographa californica multicapsid nucleopolyhedrovirus (AcMNPV) is a kind of potential biological insecticide. Ac-PK2 protein encoded by orf123 in AcMNPV genome can inhibit eIF2α family kinases to increase viral adaptation in vivo. In our previous study, it was found that recombinant AcMNPV-PK2-EGFP showed high virulence and anti-insect activity against Sf9 cells and Spodoptera exigua larvae. In this study, we investigated the function of Ac-PK2 protein in the insecticidal activity of AcMNPV and the anti-insect mechanism. AcMNPV-PK2-EGFP up-regulated the expression of Ac-pk2 gene in midgut and nerve cord in infected Spodoptera exigua larvae, compared with these in wild-type treatment group. Transcriptional level of BmK IT and detoxication related genes in epidermis, midgut and nerve cord was detected by quantitative PCR. Phenoloxidase activity assay showed that the insect’s humoral immunity was affected by AcMNPV-PK2-EGFP in a time-effect relationship. Western blot analysis of P53 protein indicated the apoptotic level in the midgut tissue was higher in AcMNPV-BmK IT and AcMNPV-PK2-EGFP co-infeced Spodoptera exigua larvae than that in other treatment groups at 4 h and 8 h postinfection. These results provided a theoretical basis to study the application of AcMNPV-PK2-EGFP as a biological insecticide.